I started using an adult sized pacifier because of air leakage through my mouth while on a CPAP machine. I don't like the full face mask and someone suggested this idea. I went from 13-15 (an air leakage score, where 20 is perfect) to 18-20 immediately, with 20 being more the rule than the exception, immediately after doing so.
Additionally, prior to the pacifier, I would awaken 2 to 3 times a night. With it, I sleep the whole night through.
So, for me it had definite benefits.
I can see how some find it has some addictive aspects to it as I've found it to be instantly calming after placing it in my mouth prior to sleep. I've tried it when occasionally napping, not wanting to go through the steps to hook up my CPAP machine and my fiance told me that it had significantly decreased my snoring, even when not hooked up. Note, too, that I use a chinstrap which, in addition to preventing my jaw from dropping, works to keep the pacifier in my mouth when used. In fact, with very rare exceptions, it stays put the entire time I'm asleep and I wake up with it still there. In those rare exceptions, my air leakage jumped up and I would awaken. Once I realized the problem, I'd find it easily enough (now I have 3...just in case) and put it back in my mouth, falling asleep within minutes.
So, not sure if the lack of a chinstrap would affect anyone's results, but with it, I find it an absolute necessity.
The only possible "negative" is that I've noted a slight change in my occlusion in that my upper teeth are now slightly forward. I had asked my dentist to measure the overjet and, whereas it was once 1-1/2 millimeters it's now 2.8 so it's a small change and, for me, actually better because my upper teeth used to hit my lowers occasionally, something that doesn't occur anymore.