Intel Sandy Bridge RC6 Is Good To Go
Nexuiz was a similar story... The power consumption when running this once-popular open-source first person shooter went up by about 30% (26 Watts to 34 Watts) while the frame-rate performance went up by 22%. The deep/deepest RC6 states still were of no significant benefit.
With VDrift having RC6 on causes the power consumption to go up by 29% while the frame-rate for this OpenGL racing game went up by just 10%.