Just wondering on opinions. I read good things as well as opinions that it's nothing but ... (add whatever dirty words you wish :) ). I personally tried Parelli and didn't like it much, however I started Clinton Anderson techniques recently with the problem mare, and they seem to be helping out (although progress is very-very slow).
What I have to admit though Parelli, Clinton, etc. etc. have really amazing horses to demonstrate (like riding without bridle, turning and lunging free in field, and so on). I don't think those trainers run to the barn at nights (when noone see them) and use some different methods on those horses than they demonstrate to public. Lol!