Here are some results so far on a dedicated miner:

ASRock 870 Extreme 3 R2.0
Athlon II X3 455
Two cores disabled
CPU voltage dropped by 0.1V
1 stick of DDR3 1066
Seasonic X-1250 PSU (80 Plus Gold)
Windows 7 64 bit
60GB Vertex 2 SSD

All of my dedicated miners are usually using a headless Ubuntu install on a flash drive, but since there probably aren't any programs for Linux that will allow me to change the clocks/voltage on these cards yet (besides what's allowed in aticonfig), I'm using Windows to test this.

2202 Mhash/sec @ 583 watts -- 3.77Mhash/watt  (962 mV, 975Mhz/160Mhz)
2106 Mhash/sec @ 553 watts -- 3.80Mhash/watt  (949 mV, 925Mhz/160Mhz)
2134 Mhash/sec @ 528 watts -- 4.04Mhash/watt  (931 mV, 925Mhz/160Mhz)  (one of my cards will not stay stable at this voltage though.  The other 3 are solid.)
2060 Mhash/sec @ 498 watts -- 4.13Mhash/watt  (918 mV, 900Mhz/160Mhz)  (all cards stable)

If you still think these cards aren't efficient, you're drunk.  If they were still using VLIW, they'd be insane at hashing.  All GPUs show 99 percent utilization.  If small improvements can be made to the miner kernels, efficiency will be further improved.

I've got a small external fan blowing on the rig (as with all of my mining rigs).  The temps on these cards while mining at 2060 Mhash/sec are 63/64/65/61C.  The fan speeds on auto are adjusting to 30/30/30/27% respectively.

All wattages were read with a Kill-a-watt (which makes the measurements on the AC side, of course).