I generally approach these kinds of methods with some skepticism - it is a bit 7-habits-ish - but one thing I did like about this one was that you could look at it as "design patterns for productive meetings", in that you could ask yourself what the goal of the meeting was and work from there to identify the right way to structure it. However I definitely attended too many meetings where the goal ended up being following the 6TH plan to the death rather than reaching a real goal.
I can understand the philosophical underpinnings, but honestly, it smells of 7-Habits-esque management "science" , and worse, a pure sales ploy for consulting.
At least 5-Whys ( http://en.wikipedia.org/wiki/5_Whys ) and Six Sigma ( http://en.wikipedia.org/wiki/Six_Sigma ) have show actual quantifiable improvements in industry.
Just as "brainstorming" is just a way of saying don't jump down my throat with questions and problems when I'm trying to think, the six hats system lets people say in a meeting "I have a bad feeling about this" and acknowledge their feelings rather than try to shoot it down technically because vague misgivings aren't as valued as they should be.
 Apparently brainstorming doesn't work, though I think the research compared people coming up with ideas alone, whereas brainstorming is supposed to make communal idea generation better. Maybe it still does that, but still can't beat independant idea generation.
Why do I care what business self-help books he likes ?