Personally I love the Parelli 7 games and groundwork. It has helped me tremendously with my geldings, an aggressive mare, and I have seen it help a friend of mine who was ready to sell her horse because of a dangerous rearing problem. The main reason I started with the natural horsemanship was because of the dead head robots most trainers ride. I'm sorry but I love my horse for being a horse not a mindless slave. I will admit Parelli throws A LOT of "buy this" in with his training, and I do like using other as well John Lyons, Craig Cameron, Monty Roberts etc. just because I do like certain aspects of each of their training.
Its a lot like nuts and bolts. if the riders nuts, the horse bolts -Nicholas Evans