There is nothing exciting to see with Warsow on R300g and these two R500 generation ATI graphics cards.

Xonotic with low quality settings causes the Mesa 8.1-devel performance to regress for both Radeon X1000 series graphics cards.

Compared to Xonotic at 1280 x 1024, when running Xonotic with still low quality settings but at 1920 x 1080, it causes the Radeon X1800XL to drop in speed on Mesa 8.1-devel while this time the X1950PRO manages to run measurably faster.

Mesa 8.1-devel doesn't cause any large performance improvements like can be seen for some hardware on the newer R600g Gallium3D driver, but that's because the R300g driver is basically in a mature state and isn't seeing active work like the contributions still being made to the open-source Radeon HD 2000 through HD 6000 driver. However, it does appear that there are some Mesa regressions namely affecting at least the higher-end Radeon X1950PRO graphics card for this next Mesa release due out in August.