Eeek. I tried Paintball2 on it, and it did run. However, it was opengl->d3d wrapped, even in fullscreen mode, which, to put it mildly, sucked. Bad. Not only were the framerates terrible, but it actually messed up the texture alignment and stuff. Like half an object would be textured correctly, and the other half would be all screwed up. It did this both with and without the nVidia drivers installed.
Also, Vista is slow and has like 5 confirmation dialogs for everything you try to do. It's like browsing the Internet without a popup blocker! I won't be updating to Vista for a long time.