So, mana burn's officially gone. Braid of Fire, Eladamri's Vineyard, and things of that sort just becamse TOTALLY new cards. I'd suggest snapping up a set or two of Braid of Fire, just in case someone figures out a way to abuse tons of free mana in a red deck. Bear in mind that mana now empties from the pool after each step AND phase, so no upkeep floating into draw shenanigans. The symmetrical effect of Vineyard makes it more dangerous, but its still a totally new space to work with. I'd see if those are cheap too.