shows that it is quite complete, though one of the devs told us that PM is complicated since it reaches in every other function (flickering problems when reclocking memory and so on). But I guess you should give it a shot.
I should test it the coming days. At the moment I still have fglrx on my HD3870, but I can compare whole system power usage the next days with the free driver set.
(b.t.w. Catalyst on WXP vs. Linux fglrx shows all the time about 5W more usage on Windows (whole system), I wonder where that comes from (might also be background programs))
CPU-utilization during tests