Lauri published the patch-set this morning to the Mesa mailing list that adds post-processing support to all Gallium3D drivers (previously part of this Git branch). Along with adding in the underlying infrastructure, the patch-set adds in three color filters, two versions of MLAA, and a cell-shading filter. These patches are built upon work previously done by Lauri this summer for ROUND support in the Gallium3D drivers, among other work.
In terms of the drivers then supporting morphological anti-aliasing during the post-processing pass, the Softpipe and LLVMpipe drivers are reported to be working fine. The Nouveau and R600g drivers currently have bugs with MLAA while the R300g driver doesn't have the required ROUND support at this time. No other Gallium3D drivers have been tested.
Adding in the post-processing infrastructure and the various filters is spanned across a set of 11 patches. Hopefully the bugs will be worked out soon and they will be in shape to be merged to master, so that this can be marked off as a successful Google Summer of Code project. Hopefully Kasanen sticks around and keeps contributing to Mesa.