I've used them and they do work. That said I'm not ready to install the two I would need. I guess I've known about them since the mid 70's when Walder first introduced them. For my use simple preventers lead well forward are adequate. Perhaps if I did more directly downwind (wing & wing) they would more appealing.

An observation - If it isn't adjusted it can be worse than not having it. If too tight, you can't jibe, if too loose there is a false feeling of security. It can also put a heavy load on the gooseneck, again an operator situation.