[H]ard|OCP has a short Q&A article about ATi's drivers under Linux. "I just want to know why the performance under Linux as far as 3D goes is subpar to the Windows counterpart? - Why don't the Linux drivers perform up to par with the Windows drivers in so many situations (such as UT2K3)?" Our most important target currently is stability. As the drivers mature we will spend increasing time on performance tuning. Since our drivers are relatively young, we have a lot of ground to cover. A very good read for the alternative OS crowd, or anyone looking to get into Linux. Read it all here.
Thanks for the great read, B. It's also worth noting that in contrast, the nVidia drivers for Linux are fast, stable, and generally very well-developed.