That's purely a software/OS issue though.
My current desktop has been installed many years ago (using a single floppy to fire up the network-install, if you can believe that these days ) on a 366 MHz Celeron with 3 IBM DNES SCSI drives and went through a PIII to a 2.4 Ghz P4 with a Seagate Cheetah 15K drive (and some IDE drives for storage). From there I moved it to the current box 1.5 years ago, a E6700 Core 2 Duo having a RAID1 of 2 WD740ADFD Raptors (and a RAID6 of 6 WD5000YS RE2's for storage) on a 3ware controller. Did the move quickly in 1-2 days without any problems.
Hehe yes, before the current box, I haven't been accepting anything but good SCSI drives where performance and reliability matters either. But with the ever increasing prices of SCSI, the Raptors on a 3ware did sound like a good alternative, and oh yes, they are.
Its just a shame that I do have an unused Cheetah lying around now.
My favourite real-world "benchmark" is firing up the GIMP (which loads a whole slew of plugins on startup). On my laptop (1.5 Ghz G4, Hitachi Travelstar 7K100) it takes 30s the first time, 6-7s when cached, on the desktop 3-4s the first time, 2s when its cached. The Core 2 Duo is obviously way faster, but it also shows that a fast disk does go a long way.