This afternoon two patches hit the xorg-devel list that were written by Robert Morell and reviewed by Aaron Plattner. Both Morell and Plattner are NVIDIA employees. One of the patches is to cleanup of use of improper types in size calculation with the RENDER extension. The second RENDER patch is more important and it adds PanoramiX wrappers for gradients and solid fills with Xinerama.
This isn't the only recent X Render extension work by NVIDIA, but last month Aaron Plattner had forked Zack Rusin's X Render benchmark to add in support for CA mask and convolution tests, among other improvements. A NVIDIA engineer then called for this improved X Render benchmark to be included in the Phoronix Test Suite.
No major X Render improvements have been spotted yet in the NVIDIA 195.xx beta drivers (Update: The latest NVIDIA 195.30 beta driver actually carries many RENDER updates) so perhaps this is all work building up for a major 200.xx series release. Besides those calling for NVIDIA to support an open-source strategy, the only other real issues being brought up in regards to NVIDIA's binary Linux driver in the aforementioned thread have been improved suspend support and proper RandR support, which NVIDIA is working to fix.