My Macbook Alu 08 was a fantastic gaming companion (Along side with the best work companion I have ever used, and I have worked with loads of machines).
It has a 2.0 GHz CPU with 2 GB of ram and a brilliant 9400m.
Here are the games I used to play on it:
Garrys Mod (I used to love that game. Played it allot maxed out perfectly)
Minecraft (Maxed out perfectly, but now, my Macbooks Logic Board is failing I think so the performance on everything is going down.)
CSS (Same as Garrys Mod)
Terraria *Perfect*
GTA 4 (Very very playable on low settings @ 800 x 600)
A little bit of game dev (which it did fine)
WOW worked fine maxed (I think)
This was all under boot camp btw. I did try some of these games (Gmod, CSS and Terraria) but they only run very well under Bootcamp, so if I where you i would stick to bootcamp.
Anyway, thats that. I would wait for a MBP with a dedicated GPU.
Thats your best bet. Its sad really that Apple put the HD3000 in the new 13 Macbooks

(I have heard they arent as bad as people make them out to be, but my freind had a Acer laptop with one in and it was pretty awful).
All this is my own opinion and experience.
Anyway, thats all.