I am running Win 7 RC, and for me the performance is superb. If you didn't update video drivers like Zanthor mentioned, make sure to do that. The ones that come with Win 7 RC may BSOD you Of course, I've had the newest NVIDIA drivers cutting out on me and giving the "driver stopped but recovered" thing during play, maybe 3-4 times over the last week. That's about the only issue I've had.