I agree with you John, own a couple of them and just do not believe in them. I feel there are much better ways of cutting circles if that is what one is going to do.
Steve your opinion matters highly. you are respected as a professional and john is right on topic. Allot of these tools are gimmicks we all buy them one time or another. John I don't like allot of them. BUT there's is always room for new innovation. Like the Kool glide, Seamer down now and other great tools coming along.
No I don't use them now, 25 + years ago I tried 2 different type, one with the small single blade with the center pivot pin and the other had a 3 in round razor blade in it that just took a quarter turn to cut. wow was that one was dangerous.. I have better luck counting rows and making duct tape templates for a lot better looking repair.