My 9-month-old Schnoodle barked incessantly at me at people coming to the door, etc. I used it twice with the command "no barking." Followed by heaps of "good boy" praise.
Then 3 times without actually pressing the button. The barking just stopped instantly.
Now I just point my finger and say "no barking" (which is very rare). It worked for us!
He had a barking fit at the groomers and I pointed her black stapler at him and told him "no barking" and he stopped immediately. So the training definitely is in the consistency. He remembers the device. I'm happy, he's happy. It worked for me and my puppy! I haven't needed to use it since. Worth it!
Bottom Line: Yes, I would recommend this to a friend