Theros is looking sweeter and sweeter. I've been keeping up with the spoilers, and the more I see, the more I like it. A few of the cards are overcosted in mana - but that's always the case - and a few of the cards are just incredible. Including some reprints like Thoughtseize, which is just incredible.
I'm currently torn between playing Green and Black.
Green because it's built partly around hot damn amazons, contains some really cool monsters, and because I love and adore ramping decks.
Black because aside from a Zendikar vampire deck I have lying around, I've never played a proper black deck. And with the strong Greek underworld theme, they have some really interesting and unique cards. I especially love Rescue from the Underworld, where you sacrifice a creature in other to bring back another create and the sacrificed creature in your next turn. The only concern I have about black is what types of creatures they get. I'm not interested in zombies, or demons, or harpies. The nymph they've spoiled so far is awesome. If they get more black-themed nymphs, that would be awesome. Also, spirits. I will be so disappointed if there isn't a Charon/ferryman card.
I've promised myself I won't play white/red aggro ( on account of having a perfectly kick-ass Boros deck lying around ), or blue ( because some of my favorite decks are blue, and it's pretty much my favorite playstyle, and I've played way too much blue. I'm also not very good at constructing blue decks, apparently. ).
In the end, though, I'll probably make way too many decks for my own good.