The problem is that ATI fglrx drivers do not work with current Xorg server (graphic environment for Linux, to say it simple). I won't bore you with technical details - If you like to know more just read some external sources:
- bug report in Debian BTS
- forum rage3d
- official ATI BTS

What I want to say here is that I am really disappointed about how ATI treats their users. Knowing their previous attitude towards Linux community (ATI drivers for amd64 architecture were released much later than nVidia ones) I expect that solving this problem shall take them a lot of time. If I were to bet I would tell sth about 3 months or more. You can track the case on your own using the last from above links.

One can say that Linux market is still too small to be considered seriously. But even 1% of their income from graphic cards would be much more than sufficient for hiring a guy like Keith Packard to provide a much better support. And one should know that more than 1% PC users have Linux on their boxes. I would estimate it as something between 10% and 15%. It's quite a big share to have an income. Additionally, I heard some rumor that Windows Vista will trigger more people to switching to Linux. So, it is unwise to disregard this part of market.

I hoped that buying ATI by AMD will change things for the better - as far as I know AMD has a good position in Linux community. We will see how this case would be handled. But so far I still advise against ATI if you want to buy a graphic card for Linux. Even nVidia has better drivers and better attitude towards Linux community. But if I want to buy a new card just now I would buy an Intel product - it is the place where Keith Packard works