Works out of the box.

3D is disabled.

Install the "ATI/AMD Proprietary FGLRX Graphics Driver".

Source: ATI Radeon Linux Display

Download: ATI Driver Installer (ati-driver-installer-11-12-x86.x86_64.run)

Additional Source: AMD Support & Drivers

Side effects:
Default desktop GNOME3 and Cinnamon shows garbled menu captions. Some windows are warped.

Image care of Stereotypical:

See original post from here.

Temporary Solution:
Choose MATE or the GNOME2 Classic desktop on the login screen. Don't use the GNOME3 desktop or the Cinnamon desktop (if installed).