Mesa 9.2 contains a heck of a lot of improvements from better OpenGL support to new Gallium3D features to performance improvements in the hardware driver. If you've been following all of the Phoronix articles in recent months you should know very well what to expect, but if you haven't, in the coming days I'll write up some "recap" articles covering this six-month update to Mesa.
Anyhow, for those sticking to tagged releases rather than living by Git master, Mesa 9.2 RC1 is now available for testing per this release announcement.
Ian Romanick originally planned to do release candidates a few weeks back following the Mesa 9.2 branching, but he claims to have forgot about them. Ian still wants to march ahead with the Mesa 9.2 release on Thursday, but is open to delaying the release if feedback suggests so based upon the forgotten RC builds.