Just slapping on my favorite GPU won't exactly make a gaming beast out of a Mac, so your question is a little misleading. There would be little/no overclocking potential with their motherboards, and you're not fitting high end hardware into a Mac Mini or and iMac, so at that point it really doesn't even matter if it's Apple branded hardware since it isn't going to be slim and pretty. So you're really just asking if people, gamers specifically, like OSX or Win7. Though in that two-way question, I'd still take Win7. If I'm going to pay for either one I may as well get the one I'm most used to. Linux is great because it's free and I'm still decently comfortable using it.