Since I do not consider speed as important as quality, I will not discuss it. If one already has an scsi card and wants to add this scanner to the card, one should find out whether the scanner is compatible with the card. Unless one can install it oneself and is familiar with the often complicated process, I often advise people to pay a little more and order it through a local store that will check it out and configure it to one's system. Most of the major companies make these low end but perfectly adequate scanners. If one wants more speed and more bit depth, then a 30 bit scanner would probably accomplish this goal.
Optical resolution is built into the hardware while interpolated resolution is a matter of software.
One should choose a scanner with a minimum optical resolution of 300 x 600. Unfortunately, too often manufacturers and some authors refer to the input in terms of dpi. What needs to be remembered is that the image's resolution should be able to be 300 dpi or 150 lpi. Unless one is using line art, a final output of 150 lpi or 300 dpi is sufficient for most work including commercial output. I believe this item is the least stressed in advertisements and the least understood.