I have lots of prospecting friends from Calif and Nevada to Arizona and a whole lot of them have put dogs through the training and swear by it. Every year on my AZ prospecting trip I wonder if we will encounter the fangy beasts, so far all is well.
But I do carry a weapon with me and every other round is a snake load. Personally I would only shoot one if we could not avoid it.
And my dog has not had the training.