Better than I thought....
My Macbook Air 3,2 (OS X 10.6.8) is not widely considered as a gaming machine. But the performance here would convince you otherwise; I can toy around with the graphic options without any great decline in performance. Bioshock (the first one) performs even better. There are pre-setting for my Xbox 360 USB controller, and I have experienced no crashes so far.
My only complaint has nothing to do with performance: there are no cheat codes for Mac, and this game is not so easy. Still, though, its quite a drawback knowing I will not be able to see much of this game because it gets too difficult to play because there is no console, no cheat codes, no trainers, and no (accessible) .ini files to alter in this Mac version.
I eat flies about Borderlands Game Of The Year