I made s set for my Vortex that's pretty much like the commercial model. Can't notice much difference in noise reduction but they are handy to check on brace height. Would I buy a set? No.
Limbsavers (slich on bow version) didn't do much for noise reduction either. According to a reply I got from Excal, they decrease speed by approx 10 fps.

At the ranges I shoot deer the noise bothers me alot more than them.. It's the arrow they don't seem to like. Everything I have shot with the Pheonix this year has been under 20 yards and they don't even have time to start cocking those legs..

I wonder how much sooner the sound gets to a deer than an arrow at 20 yards.........................................Spee d of sound about 700fps or sumpin vs. yada yada == I guess I have no idea..

i broke down and made a crude set for my vixen at a whole lot cheaper cost than what what the ready-made will run.