For another ioquake3 game, with World of Padman the performance improvement with this user-space OpenGL library upgrade equated to a 6% improvement.
Lastly, for Urban Terror there is a 10% boost under Mesa 8.0.
On average the Mesa 8.0 release is easily 6~10% faster for many OpenGL applications compared to the Mesa 7.11 release for current-generation Intel Sandy Bridge hardware. It is not only within Mesa where Intel has been focusing upon performance optimizations, but ongoing work is taking place within the Intel Linux kernel DRM and the xf86-video-intel DDX (namely in the form of Glamor and SNA acceleration).
Beyond the performance going up, the Sandy Bridge graphics are supportive of OpenGL 3.0 / GL Shading Language (GLSL) 1.30 with this forthcoming open-source release. Previous generations of Intel graphics hardware have not received as many enhancements as Sandy Bridge, but still should be in good standing for their hardware capabilities. It is also reported that Intel Ivy Bridge Linux graphics are already shining, but we will need to wait a bit longer to see for ourselves.
If you have any questions for Intel about their Linux support, give them your questions and feedback.