I believe that most training books or videos have something to offer. You find bits and pieces here and there and put it all together into your own approach. That said, I got a lot out of his book. Is it a great stand-alone reference to use for training a HT or FT dog? Absolutely not. Would it be a good reference for someone training an all-around gundog? I think so.
Like most here, I think the Lardy and Graham stuff is the most useful source of info on training the technical aspect of the retriever games. But I have also read the Dobbs book, the British stuff, Wolters, Tarrant, Goodwin, Gould, and a bunch of others including several non-retriever books. I get something out of it all.
There are lots of great trainers out there that specialize in FTs and HTs but I think if I were a guy looking for somebody to train a good solid gundog, I would probably take a good hard look at Butch. It seems to me that he has a pretty good handle on what most hunters really need in a dog. One man's opinion.