SCSI is for people with money... it is much faster though. The sustained transfer rate on most IDE drives is somewhere around 20 mb/p and the fastest (ibm 75GXP) does around 30 while scsi drives can sustain around 30, the highest i believe is at 40 or so for now. But the difference is also in bursts, ide drives burst up to 66mb/p while scsi can go up to 160 mb/p (assuming u have ultra wide and a 64 bit pci bus) I don't know that the ata 100 drive can even burst upto 100, anyone know? The difference is noticeable between ide and scsi but for the money... i don't know.