My Dad bought one, from a newspaper, it does the job and is a lot quicker than a conventional scanner with slide adapter as you can put in a few slides in together and slide the holder along. It isn't digital photo quality but it is okay and has meant that I now hold a copy of all his slides he took of the family on one of my hard drives, from which I will make copies for my brother and sister, and has given a new lease of life for them. I intend putting them on to a dvd movie at some point. Some of the slides were quite dark so the quality does depend on the quality of the slide/photo in the first place.
For years they have not been viewed now they can be so I think they are a good idea.