Unfortunately, the open-source graphics driver with Linux 2.6.38 final is still not in good shape. A few open-source games will work like before, but the bugs that hit the Radeon TTM bug persist. However, with the Linux 2.6.38 kernel and the "drm/radeon: fix problem with changing active VRAM size" patch, the system will simply restart right away when running a game like World of Padman.
Here is the bug from last weekend being talked about. Simply using Compiz and some games at least won't cause this memory management issue so you're fine there with very light usage, but otherwise right away when launching the game you will lose your system.
No new patches have been published yet but hopefully the Radeon TTM support is properly fixed in Linux 2.6.39 and that a fix also works its way back into a Linux 2.6.38.x point release. Tomorrow the first AMD Fusion E-350 processing benchmarks should be published on Phoronix.