My 11" Base MBA plays Portal 2 perfect in Windows. CPU load stays around 40-60%, only about 1-1.5GB RAM used peak in W7 x64. With the 320M at stock clocks, it plays it with everything cranked, no issues at all. 16xQAA, Very High, ETC. I have the 'battery saver' on that limits to to 30 FPS, since it looks perfectly fine to me like that, and then it is almost silent. This game is very efficient. The GPU load never goes above about 50% load at 30 FPS, it keeps flipping between idle and load 3D clocks. It does closer to 60-70 FPS without the limiter, and closer to 80 fps with the video card over clocked to 575/1300 which is where I normally run it in Windows. But this increases power consumption, heat output, and noise... So I just play it at stock clocks and 30 FPS.