The prong collar saves my a** with Bo. To be honest, we were somewhat lazy walking him as a puppy. We have a huge backyard and did leash training there, and somehow I thought that would be enough. Until real life stimuli were involved. Ha!
He is a puller, and he suffers more without a prong than with. The prong is like a gentle reminder, "Wait, I'm choking myself, and it kind of hurts!" Without it, that darn dog could run/walk 10 miles and still pull!
I felt really bad about it too, when I first got one (my first obedience class instructor turned me on, but still). They sell plastic ones now, that look more like regular collars. Makes it look less like you are walking some vicious dog (which makes me feel better on the inside).