Ken:

It funny you should compare the STS with Mathews. I keep feeling the same way about them both. With all the praise the STS gets on AT, I feel that I have to try it again, just to see what I am doing wrong. They mention a "sweet spot", which I have searched for, and experimented as much as I know how to do. I still hear a slap. Not really loud, not that much louder than the bow is without it, but not quieter. When I first shot the bow with the STS, I had a Whisker Biscuit rest, and it seemed to shoot very well. I have since re-installed a drop away, and I think I can group a bit better without the STS. Not sure why. The way guys talk about STS on AT, I guess I was just expecting more of a difference. When others who have shot it claim the same results I had - not really quieter, just different, it at least makes me think I'm not nuts (at least temporarily). I would think there would be at least some potential for downward nock travel for a few inches after the string hits the STS. I guess it seems to work better for some than others.
My impressions of my bow without the STS is that it is quiet enough, forgiving enough, and more accurate than the crackpot behind the string.[8D]