Quoting Karanbir Singh mail-lists@karan.org:
iirc, its just dri that causes issues, disabling dri and using the radeon driver directly seems to keep the system usable.
That's a separate issue.
"Stable" open source DRI drivers are available up to RV280 chipset (RV100, R100 and RV200 chipsets using radeon driver, R200 to RV280 using r200 driver). RV200 is really R100 on steroids, hence it uses radeon driver. X300 has RV370 chipset. The r300 driver that should support 3xx and (at least some) 4xx chipsets is still under development (experimental version available). AFAIK, still nothing for 5xx chipsets (X1x00 cards) -- maybe r300 will support those too, or maybe it supports them even now, I don't know. The r300 website clearly states "The source code on this website may damage your hardware". I might give it a try one of these days ;-)
If somebody is having issues with X300 card, it's not DRI. Since neither radeon or r200 DRI device drivers support this card (not to be confused with 2D radeon module for X server which is used for all ATI Radeon cards). William has Radeon 7000/VE (according to his lspci output), which uses RV100 chipset (and optionally radeon DRI device driver, if DRI is enabled). That card works fine without DRI, and some versions of it work with DRI too. I have one Radeon 7000 card that works correctly with DRI (however, it's PCI card, not AGP, so somewhat slower) -- seems like I'm an lucky bastard ;-)