After the Intel kernel DRM tests, I ran some quick tests comparing Mesa 8.0 and the Mesa 8.1-devel Git state to see if there are any noteworthy performance boosts visible there yet in the usual stack of Phoronix Test Suite / OpenBenchmarking.org test profiles.
There's still several months left until Mesa 8.1 will be officially released, but at the moment for Sandy Bridge there doesn't appear to be any notable OpenGL performance boosts.