Although I no longer use this rest, I obtained the tightest groups ever when I had it on my bow. Actually, all of the drop aways I've tried, have tightened my groups. I no longer use it, because it just seemed too big for me. Not that it was really in the way, but I just like prong style drop aways with the turned down V prongs. Like the Tiger Tuffs, or the GKF V launchers. They are more compact, and I know more about them. I realize that the Muzzy is a pretty tough rest, but if it ever broke on me in the woods, I'd be screwed.
Many people like the fact that the arrow can't fall off the rest, but I've NEVER had my arrow falling off the rest as a problem. Also, the reason I use the V-style prongs on my rest, is because when they are covered and silenced with suede leather, (similar to moleskin), I can honestly cant my bow parallel to the ground and the arrow WILL NOT fall off!
The Muzzy ZE is a good rest, but it just wasn't for me.
Also, KY, keep in mind that if you plan to use the Zero Effect on a Hoyt TEC riser, you will need to get the special little mounting plate from Muzzy. They probably don't cost much, but my dealer gave me a plate for free when I purchased the Zero Effect.