In the weeks leading up to the Mesa 9.1 release I published OpenGL benchmarks of Intel Sandy Bridge and Intel Ivy Bridge hardware. The open-source OpenGL driver for these two latest generations of Intel hardware were in good shape on this latest Mesa release. Made curious after the recent GL3 controversy (plus having an Arrandale system out as part of the extensive Linux x86 vs. ARM benchmarking), I ran some OpenGL tests on the Intel Core i3 330M "Arrandale" nettop.
The Core i3 330M system with its "Gen5" Ironlake graphics were tested with Ubuntu 13.04 while using the latest Git branches of Mesa as of today: Mesa 9.1 git-7a161a, Mesa 9.0.3 git-c864835, and Mesa 8.0.5 git-a8ff9a4. The full system hardware/software details can be found in full on OpenBenchmarking.org.
No other variables changed aside from the Mesa / i965 DRI driver version in between testing, which happened with the Unity desktop and Linux 3.8 kernel on an updated Ubuntu 13.04 development snapshot.
There were notable performance boosts from Mesa 8.0 to Mesa 9.0, but from Mesa 9.0 to 9.1 there isn't much of a difference to see... Much of the new OpenGL extension enablement is also only for Sandy Bridge and newer.
With OpenArena 0.8.8 there is at least a very minor performance boost for the Core i3 330M system with Mesa 9.1, but the performance even at a mere 1280 x 1024 resolution is still far from playable on Linux.
Reaction results are mixed.
There isn't anything exciting to see out of Mesa 9.1 this time around with Xonotic.
Overall, the Ironlake (Clarkdale/Arrandale CPU) graphics performance hasn't evolved much with Mesa 9.1.