<< there is very little performance to be gained by using ata100 instead of ata66 >>
You've got to look at all the pieces to the puzzle before you make that statement! The IDE controller on the motherboard in my son's PC just supported ATA66, so when his ATA66/5400rpm HDD recently crashed, I got him a Promise ATA100 card with a new ATA100/7200rpm Maxtor drive. He tells me he sees a very noticeable improvement. Of course, some (probably most) of that improvement comes from the reduced latency of the new 7200rpm drive vs his 3-yr old 5400rpm drive.