Pushed this morning were a number of MSAA-related commits by Marek. After several preparatory commits, the main commit this morning was st/dri: implement MSAA for GLX/DRI2 framebuffers. The commit message explains, "All MSAA buffers are allocated privately and resolved into the DRI-provided back and front buffers. If an MSAA visual is chosen, the buffers st/mesa receives are all multi-sample. st/mesa doesn't have access to the single-sample buffers in that case."
The end result for this work today is that multi-sample anti-aliasing (MSAA) is now working for a greater selection of OpenGL Linux games. The game cited as now working properly with MSAA on Gallium3D was Nexuiz.
MSAA in Gallium3D has been worked on within Mesa going back to 2010 while earlier this year there was more serious MSAA Mesa support going on with Intel finally getting this anti-aliasing technique working for their classic DRI driver. This summer was when Marek hooked in the Radeon Gallium3D MSAA support.