HAF, i found a fat book of his in Border's (the book store) that had alot, if not all, of his exercises in it, both on the ground and under saddle. It is excellent! It gives you very clear steps on what do do and includes a list of potential mistakes that the horse or handler can make as well as LOTS of pictures.
Having read the book i don't think his methods are aggressive at all! With all his cues he starts off small to give the horse a chance to respond lightly and then builds up to a stronger demand if the horse is stubborn or ignores you. I think that there was only one instance in the book where he actually advocated the hitting of a horse, and that was when the horse went to bite or kick, i can't remember which, and I agree. Horses are big animals and if allowed to get away with that sort of agressive behaviour they can get dangerous! Now he did not say you should beat the living daylights out of your horse, just give him a sharp smack, then resume what you were doing. It's not abuse, they're smart, they *know* why they were smacked.
In some of his other exercises he will tap the horse with the handy/carrot -stick, not to hurt them, but it's annoying and they eventually move away.
To sum it up I very much like CA's methods, he is straight-forward and easy to understand, his methods are firm but not harsh and in my opinion he's better than Parelli, but that said, different methods work for different people and different horses. But I would deffinately give him a shot! Good luck!
Sorry for the long post!!!