Jeff,
The product is a good one, and the people associated seem like very nice folks...but I do think some are getting a LITTLE carried away with the claims of performance and feel. There are a bunch of people jumping behind it with really BIG claims of performance, some are friends of the manufacturer, others are some sort of staff, so you do need to weed through the "over the top" stuff.
To say that a bow like the Allegiance with and without the STS is night and day is simply not true. It DOES make a difference, but that difference in feel is going to be proportional to how bad the vibration was to begin with. But there is no doubt it works.
I could absolutely feel a difference with my Old Glory in vibration as I am not using ANY sort of string silencers, so it soaks up that string occilation nicely and the cooresponding snap in the shot.

I don't hear any "slap" coming from the string hitting the unit either.

My interest with it was #1 If it creates more accuracy by in effect getting the arrow away cleaner and quicker.......I'm all for that.
and #2 cut down on the string vibe I was getting due to my string being bare of silencers.

It has done #2 for sure, and I really believe it has helped #1 a bit as well.

Think of it this way.....as an arrow drives through brace, the string is going with it for a few inches, and this is probably the time when we're going to screw up a shot........toward the end of the shot by dropping your arm, grip etc. If it is getting the arrow off closer to brace, it HAS to make the shot cleaner, and could actually make your bow inherently more forgiving. Technically the powerstroke ends at brace, but if a bow has the string driving 3" beyond that's another 3" that we can influence the shot before the arrow clears.

I like the product, and will continue to use it. It does just what I expected it would, and maybe what I HOPED it would.