I've never used one (don't have anybody to teach me), but I think they are appropriate for a certain percentage of dogs in limited situations. Crittering, for example, and reliability off-leash in a dog who already understands a recall. Interestingly, for those who use spray bark collars, there was a woman with a dog at our obedience class on Saturday whose other dog takes the class prior to ours. She was put away, but she's a barker, and the woman was using a remote collar with unscented spray. I have a hard time accepting the use of citronella as dog noses are *so* sensitive and the citronella takes awhile to fade away, which means the dog is still being corrected long after they've quieted. Unscented spray seemed like an interesting option.