Totally disagree!! The Hd in today’s PC's is still the slowest component and considering it's being accessed a lot in windows and when loading/running programs the speed of it is very important imho.
All my computers use 15k SCSI (Maxtor ATLAS II's and Seagate Cheetah 15K.5's) and whenever I use a friends, colleges ..etc normal computer (7.2k) the difference is massive and very frustrating.
People also think that SCSI is expensive but if you shop about you can get some great deals, my first 15K U320 setup cost about the same as a 74Gb Raptor for both the controller (Inc cable) and a 36Gb Atlas II