I also only use the OC, installed with the "nothing" skin and font height changed to 11 to match ATI's tabs. Another nifty thing is to disable the ATI tray icon from the options tab and then enable ATI tabs from the R3D tray icon (default icon can also be changed in the registry if you like).
[HKEY_LOCAL_MACHINE\SOFTWARE\Registry Tweak\ATI]
"GUID"="{700B1221-CAFF-11d1-B9DE-000000001B1B}"
"Disable"=dword:00000000