After "partially" switching to Mac (I still have a previous gaming PC around) I was desperately looking for a racing game for the Mac as NFS Shift is Windows Only.
Though there was also F1 2013 (which I love too), I decided to give GRID a shot, and it didn't dissapointed me.
The AI is kinda stupid, as others mentioned, and at times it feels too "arcade-y", but you can get pretty realistic results tinkering with the settings.
Oh, I should mention that (as almost any other game) the MacBook gets pretty hot (I got it on High settings at 1440x900, with silk-smooth 60fps), but never gets too hot to be dangerous. At any case, just get a cooling pad and you'll be fine :)

- 2,3 Ghz Ivy Bridge i7
- Nvidia 650m 512 MB
- 4 GB RAM

Amazing game, I literally spent hours non-stop playing it. Favorite civ is definitely Japan, that bushido skill really pays off later.
Totally recomended game, looking forward now to Civ Beyond Earth coming soon.