100% Windows here, although I originally discovered Dominions:PPP through a Linux gaming website....
Like Velusion, I use Windows professionally. I even have the MCSE, for whatever that's worth. And my Windows is pretty well-customized to exactly what I like. Yes, it's possible to tweak the heck out of Windows with a little bit of work.
I've tried several different flavors of Linux, and my favorite is Ubuntu. Still, though, I'm not sure that I see the huge appeal. I can get all of the cool OSS stuff for Windows, plus Windows runs all of my games. Why switch?