recently I had to switch to the gallium based r300g driver to get GLSL support, which I need for a project. And I must say I am quite impressed. It exposes all extensions necessary for OpenGL 2.1 and already seems quite stable. Although some extensions are not implemented properly yet like NPOT as they need special workarounds I think this will eventually become the most feature complete driver for radeon hardware.
But although currently compiz works as do most of the OpenGL programs, I would not reccomend using r300g for production use as it is still really slow. I know glxgears is not a benchmark, but these numbers represent the impression I got quite well
- 8200 frames in 5s (no kms + classic mesa)
- 5140 frames in 5s (kms + classic mesa)
- 2431 frames in 5s (kms + gallium)
But as r300g exposes GLSL and the adobe flash player uses that if available, HD flash movies seem smoother now. And considering that using gallium not only provides better OpenGL, but eventually also VDPAU, OpenVG, OpenCL etc. the r300g driver does a good job already. And remember all AMD cards starting from r300 will get this stuff – I hope you now see why open source drivers are important 😉