There isn't any major OpenGL performance changes to report on for Warsow, the only major game powered by the Qfusion engine.
The Xonotic performance with low quality settings is up by 36% from Mesa 7.11 to date, but from Mesa 9.0 to 9.1 there isn't any major performance evolution for Ivy Bridge.
The Xonotic performance with high quality settings was also up by 36% comparing Mesa 7.11 to 9.1, but likewise, without any major performance change since Mesa 9.0.
There's some performance improvements to find for Intel's Ivy Bridge hardware with Mesa 9.1 as shown by the results today. Aside from the performance changes there's better OpenGL coverage with support for new extensions and ongoing OpenGL 3.2~3.3 work plus other features being tackled. Perhaps more interesting though is the performance improvements to Intel's Mesa DRI driver when comparing the performance going back to Mesa 7.11 where Ivy Bridge was initially considered stable; in the past year and a half there's been many very significant performance optimizations to Intel's 2012 platform.