I have switched to Ubuntu 7.10, a few months ago.
I wanted to learn a little about linux, so I installed on a second PC. I have not even turned on my windows machine since.
I should really get around to installing on my best hardware, AM2, 2.6 Ghz, 2Gb DDR 800, ATI 3850...
My Ubuntu box, 2.0 Ghz, 2Gb DDR 400, NVIDIA 7600GS...
I don't really play any video games anymore, so I don't feel I am missing anything.