A lot of people like me use Linux a lot during the day, and see that the more you know about it the more you can earn, just based on being a sandal wearing geek! A lot of those same people have thought about using Linux at home, as their gaming platform. I know UT runs sweet as pie on Linux, and iD have ported their stuff for ages. The problem is that apart from a few exceptions like the above you seem to be stuck with games like GL Minesweeper and second rate tetris clones. There is of course a few other issues, like the way Linux is a pain to look after, with its steep learning curve.
Those clever chappies at GameSpy have put Windows and Linux side by side and decided to have a look at which is better for Joe Average gamer. While by no means the definitive article, it is a good guideline by which to judge the two side by side. For example the article says that Windows is far simpler to use, but that the user-to-user support in Linux is far and away better than in Windows. An interesting read for the sandal wearer and normal people aswell.