The idea of using functional imaging in psychiatric diagnosis - as a general concept - is reasonable enough, but the problem is that the knowledge is too poor and the technology not yet advanced enough to use this kind of stuff in a regular clinical setting. Some criticisms of Amen are posted above but the general tenor you see here seems to be pretty typical of how people feel about him: far overselling the utility of this technology, injecting his own thoughts and opinions in a pretty scientifically sketchy way, and charging people a whole lot of money for the pleasure.
Smart businessman, not so... benevolent would be the word, I guess, physician.