Starting off with the Austrian-developed CoreBreach racing game, the Ivy Bridge graphics performance is up by 46% going from Mesa 7.11 to Mesa 9.1. However, when it comes to comparing Mesa 9.0.2 to Mesa 9.1-devel, the performance is up by only 7%, but that's still very significant and moving in the right direction for Intel's Linux graphics driver.
The Nexuiz graphics performance topped out at 47 FPS in Mesa 8.0.5 but with Mesa 9.0/9.1 has been at just 16 FPS. This major drop in performance was due to MSAA (Multi-Sample Anti-Aliasing) having been implemented in Mesa 9.0 for the Intel i965 DRI driver, which the Nexuiz test is using, and explains the major drop in performance. From Mesa 9.0 to 9.1-devel there's no measurable change in the OpenGL performance.
The OpenArena graphics performance continues inching higher with succeeding Mesa releases. The Intel HD 4000 graphics performance is now up by 27% with Mesa 9.1 over Mesa 7.11, but most of that change happened when moving to Mesa 8.0. Since Mesa 9.0 six months ago, the Ivy Bridge performance for this ioquake3 game only edged higher by 3%.