Well I have a 9800pro radeon and it works fantastic. Not to mention the TUX racer. I even have a feeling that under RH 9 linux card works better than under windoze, but that very well may be because Houdini works better under linux. I've done some test under linux in dual head mode and again it was fine. Only problem is with hardware limitation that for full working dual head mode you can't go higher than 2x1024 in resolution because ati has blocked double buffering for resolutions 2x1280 and higher just to force us to buy firegl. And if you are in hardware hacking mood there is a way to turn this card into firegl that can do doublebuffered 2x1280 or higher. You must patch something on the card, replace the bios with the firegl bios and you have firegl.
Drivers have an easiest instalation i have seen among all devices that need a driver not included in distribution - meaning that for instance you dont have to compile anything. You just install rpm, run fglconfig and startx. You even have a small graphical utility that you can use for switching single/dual screen and various modes.
As for Mandrake, drivers are not compatible but that was never a problem for me. Mandrake was always too much winlike user friendly and I had a feeling i'm out of control of what's going on in os. Now, with this rh/fedora problem many users will think again about Mandrake (i know i am) and there is more than few of us rh users with ati's so i expect mandrake will soon solve the problem with drivers. I expect that because as i recall the problem with drivers was something stupid like: drivers expect to find some configurational files during installation that red hat calles "redhatsomething". Maybe problem is bigger but I'm sure they will solve it. Because of the money of course.