According to IBM the new 90um die shrink of the PowerPC 970 (new revision is called 970FX) cuts the power consumption pretty severely. Previously the 1.8GHz 970 used 51 Watts whereas now the 2.0GHz 970FX uses only 24.5 Watts.
At 1.4GHz it's only 12.3 Watts, I can see a Powerbook upgrade pretty soon...
Another change in the 970FX the bus speed which has risen to 1.1GHz from 1.0GHz (giving 8.8 GigaBytes per second).
Intel on the other hand are having the opposite problem, their die shrink is sending power consumption UP. The major difference seems to be IBMs use of SOI (Silicon On Insulator) which is preventing transistor current leakage, Intel are not using SOI so are suffering as a result, not that they appear to care.
According to rumours a while back the 970FX could go to 3GHz now if IBM wanted it to, the older 970 can go up to 2.5GHz but sucks something like 90W in the process. I'd guess the new revision could do 3GHz but it's power useage will be something in the same region.
Future is looking good for the PowerPC.
...as is overclockability!