The pentium-m(are core duo, is a dual core pentium-m) is a compeltely differant architecture than the P4, you can't compare the clock speeds directly. A 1.66ghz dual core pentium-m, will likely outperform a 2.8ghz Pentium-D dual core in a lot of things, while running much much cooler. The pentium-m is better at gaming than the netburst chips as well, and if you are doing heavy multitasking, or running SMP aware applications, the core duo will also have a good advantage over a 3.2ghz Pentium-4.
They are making some desktop boards that support core duo as well, and clock for clock that compete pretty well with AMD's X2's, you just need to OC them a little farther to reach the same clock speeds.