The z-quiet has been comfortable for me. It doesn't hurt my jaw when I sleep, and it doesn't hurt my teeth. If I were rating comfort between 1 (extremely uncomfortable) to 10 (most comfortable) I would probably put it at 7 or 8. It still moves the jaw so you can feel it, but I haven't experienced any pain with it at all in my teeth or jaw.
The only thing that it does kind of mess up is... my 'bite'. The mouthpiece pushes the bottom of your jaw outward. It does this by using your bottom teeth for leverage to push out the bottom of your jaw. When I initially wake up, my bottom teeth are actually pushed outward toward my lips very slightly. Like I said, not painful, but they do push them out. Sometimes when I am eating my morning breakfast, that slight pushing out of my bottom teeth makes it so my top and bottom teeth don't line up right for biting. It makes it so I can't bite down the whole way in the morning. It doesn't last all day but it can be a bit of a pain sometimes. Not nearly as bad as being blamed for my wife not sleeping, but a minor inconvenience.
I wanted to give an update on my snoring devices. So... the mouthguard just isn't working out. It works well. I didn't mind using it at all. The problem is with what I mentioned above in how it messes up my bite. It got really really annoying after a while. I would wake up and when I attempted to chew anything my top front teeth and bottom front teeth would land exactly on top of each other. It turns out that my bottom teeth move when I use these mouth guards.
I thought maybe the z-quiet was the problem so I actually tried another mouth guard called Snore RX. This one was much more substantial and was 'boil and bite' so it held all of your teeth like a football mouth guard. I thought this might hold my teeth in their normal position better. I tried it, it also worked for snoring, but it also still moved my teeth.
The final straw was, after a night of using the mouth guard I went to McDonalds and was eating a bacon, egg, and cheese biscuit. Each time I attempted to chew, my top and bottom front teeth just smashed into each other and grinded together. It sounded horrible, it felt horrible, it felt like I was chipping my teeth away, and I couldn't eat my biscuit without chewing in a weird way where most of the chewing was being done with my front teeth. About a week after this incident I had a cap / filling type thing that WAS on my bottom front tooth come off. It was a cap put over an old chipped tooth I had from over 20 years ago. It had stayed on all this time, and it finally came off because of this stupid anti snoring device.
So I guess if your teeth don't move like my did, it would still work... however, I don't know how you could ever figure that out ahead of time. I have been using max air nose cones every night since, but they are not as effective as the mouth guard. I am trying to make it so I can breath through my nose, because I seem to really snore most when I breathe through my mouth. I am also trying to fall asleep on my side but I usually roll on my back at some point during the night.
Anayway, I thought I had something good, but it just didn't work out. I think I am going to have to go do a sleep analysis. I was hoping to avoid that, but I guess it might finally be time if I can't figure something else out.