Nexuiz is one of the more demanding open-source Linux-native games for testing the Mesa/Gallium3D stack. With each successive Mesa release the R300g performance has improved for the driver, except for this latest code. Mesa 7.11.2 was running at around 38 FPS for the X1950PRO but with the current 7.12-devel code, it has dropped sharply to just 6 FPS, around where it was in the Mesa 7.9 days.
With the Warsow game there is not any change in performance between 7.11 and 7.12-devel, but there were not any interesting changes either in the previous Mesa releases. At the same time, the Warsow performance (a Qfusion-powered game) is quite low even for this high-end R500 GPU.
With the open-source VDrift racing game, the frame-rate on Mesa 7.12-devel is one of the cases where it is marginally up compared to 7.11 for R300g on the R500 PCI-E graphics card.