did you know that the Pentium 4's cannot process every 32-bit instruction there is?
the Sempron can process all 32-bit instructions, and it's AMD's version of the Celeron, which mind you does give pretty descent performance
the Athlon 64's can not only process all 32-bit instructions, but they can process 64-bit instructions too, plus they are less expensive than Pentium 4's
3.2GHZ P4: $380 aus (socket 478) or $355 (socket 775)
Athlon 64 3200+ socket 939: $299
Intel have got to 3.6GHZ so far, whereas Athlon 64's have got the 4000+ and FX-55
now I don't want to start a flame war with anybody, so I'll say what's fair: Pentium 4's do perform well, and are a descent CPU