OK - at first I thought this might be cruel. Then I decided that having my dog tied up on a leash while we were out "playing" in our expansive yard - never letting him run free, well...that's cruel. READ the directions completely first so you use this 100% correctly. My beagle learned the "come" command (despite failing during puppy kindergarten classes) with ONE correction. People are amazed at how well he listens now (without the collar mind you) I have used the stimulation feature a total of 2 times in the past 6 months of owning this. One time was during the very first use, the second was when he went charging down my driveway to greet someone walking by with their dog. Now, he wears the collar loosely and responds instantly to the beeping tone during times when he is too headstrong to listen to my voice commands. (beagles are not the easiest to control out doors!)
I prefer this to the invisible fence because I can take this anywhere we go (hiking, vacation, etc.)

Pros: trained my dog in 5 minutes - no joke!

Cons: NONE

we did attempt to use this for our first boxer, finding the correct setting without horrifying him wasn't fun. we called a dog trainer and she gave us much better and long lasting options to appropriately train our pet.

Pros: can't think of any

Cons: more humane ways to train a dog