Wizards did the right thing - they made the hard decision and banned what needed to be banned to keep the format from continuing in its stagnation around a single deck. Caw-Blade was the best deck by miles, and with the printing of Batterskull, its weakness to fast monored decks was all but removed.
Check out the data collected by William Spaniel on TCGPlayer. After New Phyrexia, Caw-Blade had a positive matchup against everything save Darkblade, and literally never put up a losing record on Magic Online. (Note: I typically co-write the Metagame Trends series over there.)
If you still don't think that a ban was warranted after looking at that data, then you don't understand what it takes to make a format healthy.
Unfortunately, there was a gap between the ban announcement and the time the ban takes effect. Even more awkwardly, the ban takes effect mere weeks before Magic 2012 becomes legal, so there's a Standard format which exists for two weeks.
Anyway, this weekend was the last set of events which had to suffer beneath the heel of Caw-Blade. I went to a PTQ in Nashville, and shuffled up Darkblade with 3 Phyrexian Metamorph stuffed into the maindeck. This was insanely good. Metamorph is basically a Demonic Tutor that actually casts the card you're looking for. The only catch is it can't get Jace, but that's hardly a complaint - it can achieve Stoneforge Mystic or Batterskull parity, it can get you 3 Squadron Hawks and chain to get all 4, it can turn itself into a Sun Titan or Emeria Angel to neutralize whatever your opponent thought to break the mirror with, etc. It's even insane in other matchups - I killed a Valakut player by casting two Metamorphs on the same turn copying his Inferno Titan to kill it and win the following turn. I even saved my skin by copying Ember Hauler against a monored player!
I wasn't the only person to find this innovation, either - there was a Twinblade player who was running 2 Metamorphs, and I'm fairly sure that if the broken metagame had been allowed to continue, Metamorph would have been an increasingly popular card for the Caw mirror.
The intermediate 2-week format is basically irrelevant. The second of the two weeks is prerelease weekend. In the US, the only notable events in the new format before M12 comes out are PTQs in Charlestown MA, Jacksonville AR, and Columbus OH, a couple of SCG IQs, and a TCQ in Columbus. In short, there's just not that many people who have to care about that format. Online, M12's release is delayed a little bit, so the temporary format lasts a bit longer there.
Given that we don't know all of M12 yet, it's hard to make a good analysis of the new format, but without the cards already spoiled, we can make some guesses since we still carry over 7 legal sets minus 2 cards.
Format Analysis Theory
A quick shorthand to thinking of decks in a format is to break them down into levels - which decks are there by virtue of their raw power, which decks beat those decks, and which decks beat those, and so on.
So, the "level one" decks in the new format: decks which are known to exist and have a proactive plan and don't have to be built to attack the other decks specifically, are Valakut, Vampires, Splinter Twin, Monored, Goblins, Pyromancer Ascension, Tempered Steel, Elves, and various other miscellaneous decks along those lines.
Level two decks are decks like U/B Control and U/W control, which typically have to be built in a manner which accounts for the existence of the level one decks and designed to "beat the format" rather than to be as good as it can possibly be in a vacuum.
Level three and beyond continue along this pattern, though at some point the lines blur, since the first-level decks can be stepped up to the second or third level by adjusting the build somewhat (think of Act of Aggression in monored vs Valakut or Twin), and those decks can in turn be stepped up to beat the new tech (consider Spellskite in Twin decks). This is only a useful framework for considering the decks, and simply pointing at a deck and claiming it's level X in a format doesn't actually mean anything for against it- if Valakut is level 1, but all the level 2 decks people are playing are Kor Firewalker decks instead of Leyline of Sanctity decks, then Valakut is effectively level 3 by dodging the hate. If Go for the Throat is the primary removal spell in Vampires, it nullifies Twin's attempt to go up a level by playing Spellskite.
The conventional wisdom is that Valakut is the best deck in the new format. It gets some new tools from M12, specifically the return of Rampant Growth and Rites of Flourishing. The former is almost certainly an automatic inclusion, but the second is not. Rites does compare favorably to Oracle of Mul Daya in that it doesn't die to every removal spell not named Condemn, but giving the opponent an extra draw and extra land drop is suicidal. Giving those to Red players will ensure a swift, fiery demise, and giving your opponent an extra land drop is a miserable thing to do in the Valakut mirror.
Valakut, depressingly, is a very straightforward deck with minor tweaks that merely serve to either make it more consistent or more explosive. The only real meaningful decision to make is to Lotus Cobra or not to Cobra. Given the rest of the metagame and the fact that Cobra's curve (from 2 to 4, 5 with fetchlands) doesn't fit in with what Valakut wants to do, I'd lean towards no. More on this later.
It's unclear whether this will be RUG, Grixis, or straight U/R, so expect all 3 versions to make an appearance. The question is whether the Splinter Twin deck can be reliable enough in the face of hate without Jace, the Mind Sculptor.
Carrying on from the previous format, monored is insanely powerful, and picking up Incinerate and Grim Lavamancer in M12 lets it replace some of the weaker and situational burn with even better cards. You can now run a lineup of Goblin Guide, Grim Lavamancer, and Furnace Scamp, with Spikeshot Elder being a distant 4th-place in the red 1-drop competition. The burn looks like Lightning Bolt, Incinerate, Searing Blaze, Arc Trail, Burst Lightning, Volt Charge, and Staggershock - and we haven't gotten into Shrine of Burning Rage, Koth of the Hammer, Plated Geopede, Kargan Dragonlord, and Ember Hauler yet!
There's simply far too much good red stuff to fit into a single deck. The real trick is going to be building it for the metagame. It's easy enough to stuff it all in a pile and figure out what does 20 with the fewest cards and the fewest turns, but in practice, metagaming is critical since there is some incredibly powerful hate for red in this format.
Vampires is probably the premiere aggro deck in the new format. It actually has a lot more in common with a creature-based red deck than it would appear at first glance; especially in this early metagame.
Act of Aggression
Act of Aggression is a card which serves the same role as the slightly-better Mark of Mutiny against Valakut: to kill them with their own fat after taking off about half their life total beforehand. Monored gets to take the best advantage of this thanks to the power of Teetering Peaks in conjunction with theft of Primeval Titan, but getting the fat out of the way will often let Vampires get through. But why Act over Mark in the first place? Simple - sideboard slots are a scarce resource, and the very threat of Act of Aggression shuts down Splinter Twin decks unless they've got counter mana open or Spellskite on the board... and Spellskite isn't exactly an ideal solution on their part.
For those of you who don't yet know how it works, you cast Act of Aggression on Deceiver Exarch in response to their Splinter Twin. The Twin continues to target the Exarch even though it's under your control until the end of the turn. Since Twin grants the ability to the creature, you're able to use the copy-making ability of the Exarch.
The timing is the tricky part: after the End Step begins but before the Act's effect wears off, you tap Exarch to make a token, use the token's trigger to untap Exarch, and repeat that a million times. On the last instance, just to play it a bit safer, you untap something else instead of the Exarch, then let the turn end. The tapped Exarch goes back to your opponent, but the million tokens stay on the board until the beginning of the next end step (which will usually be yours). You simply attack with the tokens and win the game.
Deck Interaction: Monored and Valakut
Act of Aggression puts Valakut in a corner. If they can't play their fatties, what can they do? Sitting back and trying to win off land drops alone certainly isn't much of an option, since that takes too long. Obstinate Baloth has seen play in Valakut-based strategies before, and is the first place to turn. Some players have advocated starting Flame Slash, which makes Baloth mediocre at best, but it's better than nothing. Creature-centric red strategies are vulnerable to Pyroclasm and Slagstorm, but time spent doing that is time not spent ramping to victory, and being at 10 life is enough to turn Act of Aggression into Hidetsugu's Second Rite if Primeval Titan hits the board, since Teetering Peaks is around. In practice, even that might not be enough life, since the Titan will also be unavailable to block whatever's on the board, and the red player may have a 4th land to spare for a Bolt or Lavamancer activation.
The popularity of red makes Lotus Cobra and Joraga Treespeaker both bad choices in Valakut, since they're likely to just get Searing Blazed out of the game. If creature-heavy builds of red, especially ones with Plated Geopede become popular, pairing Overgrown Battlement with Wall of Tanglecord starts to become an attractive option. The catch is you can't depend on the Tanglecord "making mana" since two burn spells (or one plus creature damage) can readily kill the Battlement, but it's better that the walls be burned than your face- a lesson which my round 14 opponent at Grand Prix: Atlanta certainly remembers.
Long story short, red is likely favored against the "default" Valakut deck over the course of a match, but if Valakut players start building their deck to the metagame instead of to the goldfish, it'll become a bit more even... though Red will likely be favored no matter what.
Deck interaction: Monored and Splinter Twin
The naive assumption is that this matchup is simply a race, with one player rushing to deal 20 while the other is rushing to assemble a combo.
In practice, it's a great deal deeper than that. The fact that a pair of burn spells can easily handle Deceiver Exarch means that starting turn 3 (on the draw) or 4 (on the play), the red player can simply leave 2 or more lands open, as appropriate, to burn out an endstep Exarch before the Twin player can combo out. As such, the Twin player is going to spend his early turns attempting to keep his life total up, as a traditional control deck, rather than to assemble the combo. (RUG Twin players will attempt to ramp into Inferno Titan or Consecrated Sphinx, while players that have adopted Calcite Snapper will hide behind it.) Game one, if the Twin player has managed to stabilize and get the monored player to empty his hand of burn spells on things like Titan or Sphinx, then he can use the endstep Exarch to win the game before incidental burn finishes him.
Postboard, things get even more counterintuitive. Twin cannot ever attempt to combo against monored if the red player has more mana open than the Twin player can fight countermagic through (unless he has Negate), since whereas double burn spells simply meant a dead Exarch and a wasted Twin, Act of Aggression ends the game on the spot. As such, if the Twin player has a transformative sideboard available to him, here's the spot to use it! Exarch can remain in the deck, since it serves as a fine utility creature and the red player can't simply ignore it for fear of a Twin combo (sucking burn out of his hand, or forcing him to leave mana open for the Act insta-win), but Twin can be taken out entirely! Unfortunately, Inferno Titan isn't so great either: Act of Aggression on Inferno Titan is at least 9 points of damage on the spot! Consecrated Sphinx is a bit better, since the best the red player can do with it is draw an extra card by casting Act during his own upkeep and hit for 4. Unfortunately, this also makes it a worse win condition.
So what's the Twin deck to do? Perhaps the answer is simply to go for it- a philosophy which serves combo players well from time to time. They can't always have the Force of Will for your Ad Nauseam, and they can't always have the Act of Aggression for your Deceiver Exarch. In truth, this all seems to make Spellskite absolutely mandatory. With Spellskite, the Twin combo isn't risking certain death (though Act of Aggression still stops the combo); and the burn player has to be able to deal 8 damage across 2 creatures at instant speed to stop the combo if they don't have the Act- and if they're able to deal 8 damage across 2 creatures at instant speed, they'd have already killed the Spellskite.
Deck Interaction: Vampires
If Vampires is sideboarding Act of Aggression, then everything written for monored remains true, save for one thing- Vampires doesn't have Teetering Peaks for Primeval Titan theft. However, Vampires typically has more creatures on board, so the fact that Titan can't block typically represents additional damage as well.
As for Twin, Go for the Throat can kill Deceiver Exarch while being completely immune to Spellskite, and discard spells can screw up the Twin player's attempt to sculpt a combo with some countermagic backup.
Deck Interaction: Monored and Itself or Vampires
The first thing monored players sideboard for the mirror is Vulshok Refugee. The first thing better monored players sideboard against Vulshok Refugee is Perilous Myr. The Myr is better against Vampires as well as white decks (which come later in the format analysis), so it should get the nod.
Vampires doesn't really have a great answer to monored - Kalastria Highborn is merely going to drain 2 life since it'll always die on the spot. Bloodghast keeps red from fully assuming the control role and killing everything it sees, so that's the critical card in the matchup from the vampiric perspective.
However, if the Vampires are willing to accept the Grand Compleation, then Phyrexian Obliterator is an absolutely ridiculous card to slam on the board across from a red player. Red does not have a good answer to Obliterator at all - neither Dismember nor Act of Aggression are cards that monored naturally brings in against Vampires, and bringing those in makes the deck considerably worse if the Obliterator doesn't show up.
Taking Valakut to the Next Level
Wait a second, now. If Spellskite stops Act of Aggression, and doubles as a halfway decent blocker, then why doesn't Valakut play it? Sure, it doesn't accelerate mana, but it's got to be decent out of the sideboard if Obstinate Baloth isn't enough. There may not be enough room, but it's got to be worth considering, especially if the matchup is truly as bad as it appears on paper.
The Fifth Color: Relegated to the Second Level
We've discussed every color save White. With Stoneforge Mystic[card] gone, [card]Tempered Steel and Puresteel Paladin are the two reasons to play white. However, I find it hard to believe that either of these decks is viable given this predicted list of 4 "level one" decks. Monored can easily assume a control role against both decks, boarding artifact destruction if necessary. Valakut and Twin both have the red sweepers available to them, and win reasonably quickly on their own. Tempered Steel has obvious problems with Beast Within and Nature's Claim, while the Paladin lists playing piles of 0-cost equipment is laughably bad if the Paladin dies on sight- a feat which all 4 top decks are able to pull off with little difficulty. Kemba, Kha Regent? Don't make me laugh.
But that doesn't mean we've got a 4-color game for the next few months. White has amazing tools against the top decks, and it's possible that they'll be able to shake up the format. Consider Kor Firewalker against monored, or Leyline of Sanctity against Valakut, Monored, and even Vampires! Shutting down Gatekeeper of Malakir, Kalastria Highborn, and targeted discard is a great starting point. Sure, Valakut has access to Beast Within but a blue/white deck should surely be able to protect the Leyline from that.
Looking into this a bit deeper, Day of Judgment and Gideon Jura are both fine choices against Vampires (so long as Kalastria Highborn is dealt with first) and creature-heavy Red decks. Figuring out how to fit this all together and still having a way to win the game that doesn't require tapping out and risking a loss to Splinter Twin is going to be the order of the day for control players. Twin combo itself fits into a lot of different shells, so it can be hard to build to beat it.
In a new format, there's always people trying out pet decks and oddball strategies which aren't very popular. Some of them are casual decks which can string together lucky draws to knock some people out of contention before eventually going 2-3 drop, but others are occasionally positioned to beat up on some of the most powerful archetypes in the format. Time Sieve was a great example of this: it had lopsidedly bad matchups against aggro decks, especially red ones, but had an incredibly good matchup against control decks.
Puresteel Paladin and Tempered Steel are likely going to be among the more popular fringe strategies. Given the blue Illusion lord's existence in M12, there's bound to be some people throwing together that deck with some Mana Leaks and bounce spells to play mono-colored undercosted-dude beatdown. Ezuri, Renegade Leader is quite powerful, and there's a fair number of people who will shuffle up Elves every chance they get.
Fauna Shaman and Birthing Pod will both attract players, since they both represent a very powerful engine. Don't be surprised to see Pod Allies make an appearance, or Pod alongside Master Splicer and friends.
Pyromancer Ascension gained Gitaxian Probe and M12 is bringing Visions from Beyond in addition. While neither makes up for the loss of Ponder and Time Warp is irreplaceable, some people will insist on playing this deck until they get sick of being blown out by Beast Within and other related cards.
The format looks like it will be a great deal more dynamic than the miserable "all Valakut, all the time" format the Caw-Blade supporters claimed it would be. The presence of Act of Aggression will keep Valakut in check, and the decks have a great deal of room to shift and change to target other decks. The metagame can shift rapidly merely through changing a few cards in the maindeck and tweaking the sideboard while the deck archetypes remain constant. With the tools available and the ability to wildly vary an archetype, don't be surprised if you see a matchup at 40-60 one week and 60-40 two weeks later.