Sorry, I'm another one who's anti-shock. I think it's cruel. Here is my cruelty test: Would it be morally wrong to do to a 2 year old child? If the answer is yes, don't do it to your dog (or cat, or ferret....etc).
That's a good test. I don't have children, but my dog (and cat for that matter) is equally as important to me as it would be if it were a human. I just don't see myself disrespecting my animals in any way.