well i have an ATI card, and yes it sucks. a mate of mine has a different video card and it also sucks. mdk 9.0 couldn't even run X on his. mine runs X 4.x fine, but the card claims it will work with hardware acceleration, but fails to do so. you need to turn that off (which has no GUI for doing so of course, so for newbies it sucks).
however the drivers for ATI cards in linux are reverse engineered are they not? i could be wrong but i was under the impression that the cards from ATI do not come with linux drivers and that ATI support in linux was community supported, is that right? if so then anything's a bonus after all...