David Airlie even acknowledges the small impact of the DRM changes for the Linux 3.6 merge window. Per his pull request message, "one of the smaller drm -next pulls in ages! ... but yeah fairly quiet merge this time, probably because I missed half of it!"
The key changes for the main drivers include:
Radeon - Documentation improvements, bug-fixes, ring/locking changes, PCI-E Gen 2.0, and DisplayPort fixes. For the Radeon DRM the only really big feature this time around is that it finally enables PCI Express 2.0 support by default, which can mean some nice Radeon GPU performance improvements due to the greater bandwidth.
Intel - More work on enabling Haswell, GPU reset fixes, DisplayPort fixes, and other miscellaneous work. The only main feature for Intel on Linux 3.6 is the continued work on getting Haswell up to speed for this next-generation Intel micro-architecture to be introduced in 2013.
Nouveau - There isn't anything fun for the reverse-engineered open-source NVIDIA driver in the Linux 3.6 kernel. There's some code being rewritten, but it's been postponed to the Linux 3.7 kernel. There's also still no improved power management / re-clocking and the GeForce 600 Kepler series support still requires the external microcode to be loaded.
DRM Core - clean-ups, range allocator coloring, and other small stuff.
So the only exciting stuff I see out of the Direct Rendering Manager drivers for the Linux 3.6 kernel is the Radeon PCI Express 2.0 support by default and the continued Intel work on bringing up Haswell.