I have a HD7950 which I use in both Windows Vista64 and Linux (Mint and Funtoo, both 64bit). I bought it because I wanted great compute performace for my artwork, scientific distributed computing, and a little gaming. In windows I can get what I paid for, but not in Linux. Gaming? Sure, Wine works great (usually) but I don't want to game all day. Doing 3d renders, creating new and interesting images, video and audio encoding, folding proteins, modeling weather systems, and curing cancer? I'm better off in Windows.
In Linux, every OpenCL project I find has at least one of three caveats:
No support for AMD products at all,
Support for a very limited range of AMD products,
and/or AMD products perform better in the given app in Windows than in Linux.
The reason for this given by the developers of these projects are very consistant: AMD needs to fix their drivers. A quote from http://folding.stanford.edu/home/guide/linux-install-guide/ :
"Folding on AMD GPUs is problematic in linux due to poor OpenCL driver suppport from AMD, so GPU folding on AMD hardware is not supported at this time. This could change at any time with a newer driver. Linux GPU folding is still in beta testing."
That is just one example. There are more than I would ever want to look up and post.
So, um, AMD, why don't you fix your drivers? There are millions of paying customers who can't use their products to their full potential do to artificial constraints on double presicion math. That alone will add years to some research projects. "Sorry little Timmy, the cancer took grandma before the the scientists could find a cure. If they could have done the math faster, you might have known her better." Isn't that enough?