The Radeon changes that landed in Linux 3.11 were incredibly huge due to the long-awaited Radeon DPM support that means a ton of improvements. With the Radeon DRM update is also the Radeon HD 8000 "Sea Islands" graphics card support, among other changes.
The initial Radeon changes for Linux 3.12 aren't as huge, but still noteworthy. This morning Deucher sent out 53 initial patches for the next kernel release.
The main change is owners of Radeon HD 8000 (Sea Islands / CIK) graphics processors now have ASPM (Active State Power Management) and DPM (Dynamic Power Management) support as was brought to the existing AMD GPUs on Linux 3.11. There's also changes with the removal of buffwe object copy support using the 3D engine with now relying upon the sDMA engines or CP DMA handling.
With recent kernel releases having brought new AMD hardware support, dynamic power management, and Unified Video Decoder (UVD) support, there isn't too much more to hope for at this point with the open-source Radeon Linux driver besides improved performance. (Well, KMS HDMI audio too.) On the user-space Mesa/Gallium3D side, of course performance is important but also catching up on the OpenGL support and making the OpenCL/GPGPU compute support more usable.