I just picked up a new 2.2 model today. I threw in Civ 4 to test it out at "High" for all graphics levels with top resolution, and it did beautifully; very playable.
I don't know how it would do at the larger and more progressed games (ie 10 civs all the way through to the year 2010), but I loaded some of the scenarios and it was great. I'd say it was noticably better than Civ 4 on my friend's C2D 1.83 Macbook when it's on "Low" for all settings at lowest resolution. Hope this helps.