P4 is also when they made the transition from 533MHz FSB to 800MHz FSB. The first P4s had 533 & the later ones had 800Mhz. I don't recall P4s not being that great. As a matter of fact, I built my system entirely off of the Ars Technica system guide & at that time & they recommended a P4 (3.06GHz) w/ RDRAM (PC1066) over AMD. However, P4s being used in laptops (e.g. Sony Vaio K-series) was incredibly stupid because of how much heat they generated. If I remember correctly, the AMDs were only recommended over the P4s after the first line of P4s won out.
Edit: It appears that my first P4 was actually 2.8GHz, not 3GHz. When I later upgraded to a 3GHz, I think AMD was winning the race.