Just to be clear,
the only thing 11.11c adds is Skyrim crossfire support for the 5000 series.
Here are the release notes from 11.11b:
AMD Catalyst 11.11b performance driver features:
New in Catalyst 11.11b:
Delivers AMD CrossfireX performance scaling for (Elder Scrolls Skyrim and Assassin’s Creed: Revelations)
•Elder Scrolls Skyrim
◦New in Catalyst 11.11b: Delivers AMD CrossFire performance scaling for AMD Radeon HD 6000 Series
■AMD Radeon HD 5000 CrossFire support will be supported soon in an updated driver
◦Improves performance 2-7% on single GPU configurations
◦Resolve corruption seen when enabling Multi-Sample Anti-Aliasing on the AMD Radeon HD 6970 Series
•Assassin’s Creed: Revelations
◦New in Catalyst 11.11b: Delivers AMD CrossFire performance scaling
•Batman Arkham City
◦Improves DirectX 11 performance for single GPU configurations
•Rage
◦Delivers AMD CrossfireX performance scaling
◦Resolves a number of image / stability issues seen with the title:
■Fix geometry corruption, sometimes seen in Bash TV entrance
■Fix issues with Low-memory conditions on 32bit systems.
■Fix issue with extreme corruption with missing textures on 32bit systems.
■Fix memory leaks when deleting/reusing sync objects.
■Fix hitching and pausing, especially noticeable on some Quad Core systems when doing races and Stanley Express runs.
■Fix some missing shadows
•Battlefield 3
◦Resolves intermittent corruption seen when playing the game at specific camera angles
Source:
http://support.amd.com/us/kbarticles/Pages/catalyst-1111b-performance.aspx