Civilization V MBA

My friend plays it on his 13" (1.8ghz) without a problem on low settings.

If you get the 2.0ghz i7 upgrade, I don't see why you couldn't run it at at least medium and get 35+ fps since you also have a smaller screen res.

 

It plays fine in the early game, but after you've revealed more of the map it'll slow down.

 

The fan might be a bit annoying. Consider you go from "never-haring-a-thing" to the fan being on all the time while playing.