M12 is shaping up to be an amazing core set... Titans, Gideon, new Chandra, O-Ring, Ponder, Grim Lavamancer, DoJ, and, oh yeah, Smallpox, which has dominated in various formats. Visions from Beyond is broken, and the new Phantasmal cards look cool. The Fact or Fiction on-a-stick Sphinx is nice. The new Jace will be crazy if Innistrad does in fact have Flashback as a returning keyword. New Garruk is cool, but too mana intensive, and since Mono Green pretty much sucks right now, he's underwhelming.
I like running rogue decks, mainly because they're cheap, so I run Mono Black Infect. When M12 is released, I might try a Mono Blue Beatdown deck with the Phantasmal creatures.
And @ the person who asked Grave Titan or Wurmcoil Engine in MBC, Grave Titan is a much better card.