wbmw: I don't see Banias as a contender for the desktop performance crown, at least not with the current features. Add Hyperthreading, an 800MHz FSB, and dual channel DDR memory, and then you might have a different story. Of course, once you do that, the CPU is not low power any more.
Adding 800MHz FSB would be practically trivial (well, as "trivial" as it is on the P4 *cough*), since Banias uses the exact same AGTL+ bus (slightly more sophisticated, IIRC, e.g. with disparate Vtt and Vcc).
I'm not sure what you mean by adding "dual channel DDR memory", but since Banias uses the same bus as the P4, using it with a P4 chipset would be "simple".
I think where we fundamentally disagree is in the performance potential of Banias for the immediate future.
Couple Banias with an 800MHz FSB, the i975P chipset and an L2 cache optimized for performance instead of power consumption and I sincerely believe that it would beat P4 in most benchmarks. I haven't seen any detailed SSE2 tests of Banias, so predicting performance in SSE2-optimized benchmarks is a bit of a stretch, but - overall - I really see Banias as the better chip... for the immediate future.
Looking further ahead, once both the software and hardware sides of HyperThreading improve (there are still plenty of cases today where HyperThreading mkII significantly degrades performance), P4 has more potential. Likely, the front-end will still need some work, but with the next major revision of the P4, that should be at least mostly be taken care of.
-fyo