I got a set in, and tried them. I liked them. Can't say they cut down on sound a great deal - already have a pretty quiet bow. They would be much better than brush buttons. I think they do make my bow more dead in hand at the shot.
However I took mine off and threw them away. I could not figure out how to unstring bow with them installed as per the instructions. My top loop slides down past where they mount, and is not big enough to go over them. Would have had to unstring both ends of string with the bow on a stringer, and I couldn't figure out how to do that, so I round filed them.