I've never heard of them before now. I've always bought factory manuals for every new piece of equipment, as well as parts catalog too. Those certainly are expensive, but they do save me a lot of headaches (and money) in the long run.
The web site for DIY Repr Man. doesn't give much info on their products. We'll be anxious to learn whether or not they're worthwhile. Please keep us informed it you do decide to buy them.