I use Ubuntu 12.10 with GNOME3 with no issues. I recently decided to try the Cinnamon desktop environment. It installed without issue, and I can easily log in with Cinnamon, but I get various screen issues. The resolution is at my native screen size, and the background and task bar fit my screen properly, but windows which have been set to full screen only fit the middle part of the screen. However, this appears to only be a visual issue, as I can close windows by clicking the seemingly empty space in the top-right, rather than where the close icon actually appears on the screen.
Additional information: I am using the most recent official release of the AMD Catalyst drivers. I have tried using other resolutions with no success.