Let me point out that Conroe would ONLY be 5x faster than the Northwood (which it was compared against) ONLY at running each at a specific clock cycle, because it seems a lot of you have forgotten that power useage scales nonlinearly.
Therefore, someone claimed for argument's sake, purely theoretical, that if Conroe ran at 3 Ghz for 20 watts then it would be 15 Ghz at 100 watts.
WRONG.
It would be fantastic if Conroe did run at 15 Ghz on 100 watts, but let's see what really happens when we scale:
3 - 20
6 - 50
9 - 110
12 - 180
15 - 280
Nobody's going to run a chip that will burn 280 watts at normal load.
I just gave the previous case as a theoretical example, but it is more in line with what really happens.
As such, it would be more realistic, to compare a 3 Ghz Northwood to a 2 or 2.5 Ghz Conroe that would use less than 1/5th total power of the Northwood to get the 5-1 ratio.
I state this not to bash Intel, but to provide a more correct, if not entirely precise view of looking at what Intel's people are saying.
That said, both AMD and Intel are working on low-power chips, they both have 500 Mhz chips that consume about 5 w/hr at full load and I remember reading that the Chinese developed (or stole the design for) a similar chip. There are newer technologies, or at least technologies that are now more frequently used to reduce power consumption. For what it's worth, Elpia claimed to develop a DDR3 @ 1333 Mhz on 1.5 volts that uses what they call "dual-gate transistors" to reduce current leakage. My bet is that AMD and Intel will be looking at this technology for their processors if they aren't already.
EDIT:
Except for those things I stated about the actual developments with reducing power useage, there are other factors to consider. Intel said 5x the performance per watt, the key word is performance, not Ghz. Also, I don't think they've even given us any means by which to measure their "performance per watt" so until then any theoretical speculation, including my own will be irrelevant.