| Dr. Bernstein used to be about 15 years ahead of the curve in terms of diabetes thinking. He was advocating getting off high-carb diets years before anyone else in the medical profession 'discovered' the same thing. A lot of his findings can really be boiled down to a combination of experience with medical training. Once you've had diabetes for about 5 years or so you start to realise that you actually know a heck of a lot about how your body reacts to different things, thanks to the trial and error you've been through. Bernstein's also able to explain WHY those reactions happen too.
I think he's a very useful information source and is very helpful for people starting to get a handle on their sugars. On the other hand I do think part of the regime he advocates is too much of a trade-off on quality of life - from what I've heard from (admittedly militant) supporters, he advocates what can end up being quite a restrictive diet.
My personal choice is that I'd rather run an A1c of 5.5-6.5 and eat whatever I like, rather than have an A1c of 4.5-5.5 but have to concentrate a lot more on what I eat and my condition in general. Other people will have different priorities to me and that's fine.  | 
