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Does that say 100 on it? I think that says 100. Gain 100 life.
Planeswalkers' ultimate abilities should be very good and should essentially win you the game. I don't know if this will win the game, but it will certainly help you not lose the game, and that's important.
5 Mana is a little rough, unfortunately. Ryan Bushard suggested it would be better if his second ability were a -1 but he cost 2GW to play. I don't know whether that would make him too good.
Now, you're never supposed to evaluate a planeswalker in terms of their ultimate, so let's look at the other abilities.
The first +1 lends itself to cards like Kalonian Hydra or Corpsejack Menace. That is a lot of value. That much buff is very good turn after turn, but unfortunately it does little to protect Ajani besides raise his loyalty out of Boros Charm range.
A lot of talk about his second +1 lending it toward a sort of control deck has popped up online, but I am not sure I see it. You want to draw an extra card that is Supreme Verdict, or Sphinx's Revelation or Dissolve. You don't want to put a land, a Sphinx's Revelation and a Dissolve on the bottom of your library so you can draw an Aetherling. This draws cards, but not the kind of cards control wants.
This is probably pretty good in some kind of GW token granting deck. Reap What Is Sown has never received any consideration in Constructed, though, and there is probably a reason. Post rotation, who knows? For now, you're not using this ajani to beat mono-black.
I think different types of players see different kinds of possibility in this card. If you are buying a lot of packs, this could be good because its presale price is likely to be way too high ("Jace's Law") and you can get rid of these before the price goes down. In a lot of ways, these are the worst kind of card for everyone else. Casual players will love that he gains 100 life and won't trade this for any amount. Competitive players will want to trade these away at the prerelease for its inflated price but likely won't be interested in picking them up. I am not pre-ordering this card, I will toy with it and see if any of my EDH decks want it (or if I have to make one - Uril, the Miststalker seems like a good candidate) and I am outing any I get in packs immediately.
Cool card. Lots of potential.