Ian Romanick of Intel announced the new release on the Mesa mailing list. Overall, the mailing list announcement is very basic and really informative compared to looking at the Mesa Git tree itself or reading the dozens of Phoronix articles about Mesa 9.2.
For those curious about Mesa 9.2, see the many performance improvements and new features but it's still without some implemented features mainly about its OpenGL 3.x/4.x support. There's also many other Mesa 9.2 articles on Phoronix.
The most recent Mesa 9.2 performance benchmarks were just earlier today in looking at the Radeon Gallium3D performance over the past two years. There's of course many more Phoronix tests to come but already we've been looking at the Git code for Mesa 9.3/10.0, especially as the developers are now looking at moving from a six-month release schedule to three-months in order to deliver more timely features and performance enhancements.