For those preferring to live on the stable Mesa series, Ian Romanick just announced the release of Mesa 7.10.2. This release just incorporates various bug-fixes.
still hasn't been released, which should be much more interesting with all of the performance optimizations, new OpenGL extensions, new hardware enablement, and so many other features for many of these open-source graphics drivers. But for those after the most stable and well-tested Mesa code (such as Ubuntu 11.04), Mesa 7.10.2 is here.
Among the bug-fixes this time around is an Intel Arrandale fix, shadow problems with the 0 A.D. game, R300g issues, and some GLSL bugs.
The release announcement can be found on the Mesa mailing list