I carry one, use it occasionally. Never use it if there is someone behind me. If the course is empty and I'm not in a hurry, I might use it to dig out some shag bag balls and occasionally find a new premium ball to toss in the bag.
Again, nothing wrong with having one when you need it. Just have to be smart and courteous as to when you pull it out.
Oh, and I don't think I have witnessed someone slowing down play using one at the course I generally play.