We did it as a way to get access to docs with significant experience in prescribing medications for very difficult cases, of which we have two. It yielded some insights into our two kids--the oldest, whom we thought maybe had ADHD in addition to everything else, had a brain that was so overactive it was overwhelming the frontal lobe--not the typical ADHD pattern.
It is no magic diagnostic fix, but I firmly believe that as time goes on we will see much more in the way of actual biolgoical markers for many of the mental iillnesses our kids suffer. This is I believe one of the starting points, and some of the top bipolar clinics in the country as doing imagining studies on patients.
If you are at your wit's end, and want a second opinion on medications etc, it may be worth your time. Are there other places to go, docs to see, no doubt.