When starting with Doom 3, one of the most interesting OpenGL games that is native to Linux and will work with a modern stock Mesa installation while at a decent frame-rate for newer graphics hardware, Catalyst still very much has its performance advantages. For all of the supported hardware, the Catalyst driver was several times faster than Mesa 8.0 Gallium3D. The exceptions were with the Radeon X1800XL (R500) no longer being supported by Catalyst and the Radeon HD 4670 was unstable with the proprietary driver. In terms of performance improvements when going from Mesa 7.11 to Mesa 8.0-devel with Doom 3 at 1920 x 1080, for the five Radeon graphics cards there were no major changes in performance.
When running Doom 3 at the very low resolution of 800 x 600, the only graphics card where the performance changed was with the Radeon HD 6950. With this Cayman GPU, Mesa 8.0 had boosted the frame-rate by 24%, but still the frame-rate for all of the graphics cards were well behind the Catalyst driver.