Warsow at 1920 x 1080 was still lacking any performance changes for this new Linux kernel.
Lastly, for the visually impressive Xonotic open-source FPS game, the performance was higher with the GeForce 9800GTX on the Linux 3.8 kernel compared to earlier releases. The lower-clocked NVIDIA GeForce 9800GT and GT 220 graphics cards saw no DRM Nouveau driver performance changes between Linux 3.6 and 3.8 in conjunction with the latest Mesa 9.1-devel Gallium3D driver.
The NVIDIA GeForce 9800GTX graphics card saw several performance improvements for different OpenGL games on Linux when using the still-in-development Linux 3.8 kernel. The performance improvements for the GeForce 9800GTX are very welcome except that there weren't as many performance improvements to find with the 9800GT and GT 220 graphics card when using the same kernels. This lack of improvement is likely because the GeForce 9800GTX was able to run at its higher factory-rated clock-speeds while Nouveau re-clocking failed for the two other graphics cards. Running at their slower boot clock speeds, the GeForce 9800GT and GT 220 graphics cards were bottlenecked elsewhere.
There was hope that the Linux 3.8 kernel would have better Nouveau re-clocking support, but that didn't end up materializing. With the Linux 3.7 kernel there was at least fan control support merged, which is a prerequisite for re-clocking support. The fan control support is necessary for ensuring the GPU's fan is working as it should so the GPU core will not overheat when being clocked to its high-performance state. Hopefully with the Linux 3.9 kernel we will see better re-clocking support for this reverse-engineered NVIDIA driver... Again, if you're not familiar with the Nouveau re-clocking debacle, see Nouveau Reclocking: Buggy, But Can Boost Performance and Clock-For-Clock, Nouveau Can Compete With NVIDIA's Driver.
Coming up in a few days will be Linux benchmark results comparing the latest Nouveau driver (Linux 3.8 + Mesa 9.1-devel) against NVIDIA's high performance proprietary driver.