At the moment, the fastest ATA Hard disk is the IBM 180GXP with 56 MB/s.
The 180GXP with 8 MB buffer (180 MB and 120 MB model) have also the highest score in benchmark like Sandra or ZD WinBench99).
Remaining in the IDE ATA market, only combining two drives in RAID 0, you can reach a transfer rate of 95/100 MB/s in the outer areas of the disks.
SCSI drives running at 15k rpm has a transfer rate of about 60 MB/s of sustained data rate.
there are some guy that works hours to speed up their computer to save one minute over a ten minutes job.