I had an 80 gig western digital ata100 special edition (8mb buffer) drive, and it gave great performance. It scored reughly 3600 in SANDRA 2002 storage benchmark, where my 80 gig maxtor with a 2mb buffer, but ata 133 (which isn't that big of a deal over ata100) scored 2500 in sandra.
I just bought another WD 80 gig 8mb ata100 drive two days ago and set them up in a raid 0 array, and loading programs is noticably faster, and it just scored 4600 in sandra.
What the Sandra score means in the real world is up for debate, and i would be the last person to put all my eggs in that basket, but i do notice faster load times on programs i use all the time even if i have not timed them.