Yeah, I was skeptical, too. Health problems lead me to the plan - many of the food classifications fit the way I ate anyway (I'm A pos) or were the same as recommendations I had seen elsewhere for my conditions.
There are lots of arguments floating around about scientific studies, blah, blah, blah. Personally, my bottom line is what works for me. The more I comply with plan, the more it just seems to be relevant. Even having said that, I do believe it is a work in progress and there are aspects of it I think will be revised.