Forget performance, ATI drivers are so unstable it's barely usable (eg. Gnome 3 restarting regularly, like once per hour), and that's just plain desktop apps (Vim/browser), trying to run some version of VLC from default repo instantly crashed the PC (needed to restart), when I tried to play games random graphics bugs were everywhere (texture artifacts, framebuffer not clearing properly, etc.) All distros I've tried so far have problems with closed source drivers, and the OSS ones don't have HW 3D I think because it's slow as hell. Also - you can't alt-tab from full screen games. I looked it up, found a post that started with "you need to modify your xconfig" closed the tab. I think linux needs a lot more polish to be viable for everyday use as multimedia/gaming desktop OS, I would love to ditch the windows partition and rebooting but I don't think it's going to happen soon.