Scanning and Computers
Yes, I imagine that many scanners are available from eBay and such websites.
I started way back when I had to insert a SCSI card into my MOBO in order to obtain reasonable speed. I didn't like the quality of my first scanner.
I moved to a Minolta Elite first generation film scanner and liked it. However, its resolution was low by today's standards.
Then I tried an Epson Perfection flatbed scanner which was supposed to handle all sizes of transparencies. It worked, but not as well as the Minolta.
So I decided that a dedicated slide scanner was superior and purchased a Nikon 9000 (as I have many medium format transparencies).
I don't think this Nikon works as well as the Minolta either, but it is better than the Epson flatbed. (Alas the Minolta pro scanner was discontinued by the time I purchased the Nikon.)
The primary reason I bought the Nikon was for posterity. I realized that most photographers were moving to digital and there was no future in scanning transparencies. Once you've scanned your transparencies, then the scanner becomes a paperweight. So I anticipated that the manufacturers would discontinue them.
So get in early and get out early is my advice. The link with PCs will sever with the dedicated models (maybe not the Plustek). For example, try to find a driver for the Minolta Elite for Windows 7. After Vista was released, I noticed that Nikon did not release a driver for the 9000 model. (I think that there is one now.)
In other words, changing computer O/S will make discontinued film scanners unusable. Also the software accompanying the scanner may not function with new O/S like Windows 7.
Other observations. Most scanners differentiate between Kodachrome and Ektachrome slides. That is, they use different scanning settings for Kodachrome. Secondly, none of the flatbeds I have used can scan more than one slide at a time. The tray may hold a dozen or so slides, but the user must select which slides to scan one at a time. Additionally, I have found that I have different preferences for different slides and accordingly change the scan settings as desired. You can scan everything at the same settings, but if a shot is underexposed or overexposed slightly, then your scans will likewise be uneven. That is, it is not sensible to scan every slide with the same settings and hence, it is not reasonable to expect a scanner to have a feeder system for unattended scanning and expect good results.
I do agree that the reviews of the Epson V700 and V750 indicate that these are superior scanners and as they are current machines, there should be drivers for all O/S's.