It's "fine" for WoW. But I would really suggest getting a Macbook Pro if you want to play WoW at a decent setting. The entrance to the Dark Portal (with all those meteor particles which you never notice until you play on an integrated video card) cause the whole frame rate to dip to 1 - 2 fps. No, I'm not joking about the FPS as I measured it using the build in frame rate monitor.
Don't play WoW on a Macbook. You'll stay saner that way.