I refuse to even consider handing over a system with Windows on it, because next week they'll call and expect me to fix it when some fake antivirus is asking for their credit card number or they can't figure out why their computer is so slow (because it's part of a Winbotnet sending out its share of 95% of spam emails).
PC gaming is more or less dead. The GPU is a way of running compositing window managers and hardware accelerated web browsers. Even Microsoft has to make a big stink about that now that all the Windows games are crappy console ports infected with DRM.
If we're going to play that game, I'll take real KWin compositing over Vista7's phony DWM any day, and Chromium 13 is running everything on my GPU via the free radeon driver. I don't need Idiot Exploiter 9, I have a real browser thanks.
As for games? meh, I'm happy to run Sauerbraten, Trine, a few others. Like I said, the mainstream PC game industry for Vista7 that you talk about is just crappy console ports infected with DRM that tell you to throw your PC out every year and buy a new one. (Kind of like a Mac in that regard, isn't it?).
If people were a little less thick, maybe they would just do it themselves instead of placing their computer under the control of various untrustworthy third parties and paying good money for the privilege.
BTW, my RadeonHD 5670 runs fine with the free driver stack, better than FGLRX in some cases. The real damning thing about proprietary drivers is that they won't ever use modern/safe/stable things like DRI 2 because they are afraid of leaking their Imaginary Property. The funny thing is that Nouveau manages in spite of Nvidia's "obfuscation via 12 year old DRI 1" nonsense.
If FGLRX or Nvidia work for you great, I think they are crap.