I recently bought a 5870, I use Arch linux and they ditched support for official ATI drivers last year as they are so bad. They are now maintained by a community Arch member, the problem is when I updated last it obviously didnt compile a new driver and it went menta lol...
I uninstalled the official drivers and run the opensource "radeon" driver. It's perfect for 2D desktop, video and compiz but useless for games, which doesn't bother me.
If you want great support for everything is the new nvidia 460GTX good? I know the 480GTX was hotter, larger and about £80 more expensive, thats why I bought the 5870.