Whether or not you are a fan of Linux, this article has some very valid points and is certainly worth checking out.
Anyway, my point here is that Linux shouldn't be a gaming OS afterthought. If you're going to program game software, you should consider Linux as one of the Big Three OSs: Mac, Windows, Linux. But, that's my humble opinion on the matter. Linux isn't some second rate OS that can be tossed aside by software companies because it isn't "mainstream."