Zyra is so good. Her lane control is ridiculous, as is her ability to lock enemy champions behind their own towers during team pushes. I'm enjoying her a lot
Edit: After a few more games, I think she is easily the game's most adaptable champion. I've tried a full on support build, maxing E and taking only one point in Q -- with an aggressive champion like Vayne or Twitch with you this works very, very well.
For soloing you'll want Q first before the stun for max damage potential. You can out-gun nearly everyone in the cast if you get the jump on them -- open with E into seed, followed by Q into seed, then ult. Place the ult so that if they flash backwards they still get hit (range is large enough, likely to be nerfed eventually). Insta win against damn near anyone.
If you're about to be ganked, try E --> seed --> ult and you'll likely get out, even against two or three.