I have heard that prescotts run very hot and at the moment they have no significant performance increase over the P4 3.2 Ghz @ 800 FSB (130 nm process) The prescotts use a 90 nm process but has an even longer pipeline so overall it's about the same.
My recomendation, stay away and go Athlon 64. When Win XP 64 bit comes out, it will be like a free hardware upgrade. You would have to pay for the OS though