Only one experience with a glory hole. It was back when I was in the Navy. I used to regularly catch Greyhound busses to and from Norfolk, Va. The Greyhound station in Washington DC was located just a couple of blocks from a seedy section of town where they had quite a few adult bookstores. I was watching a video in a private booth when the urge overcame me and I pulled down my pants and started jerking off. A minute or so later I saw some light come into my booth from next door and that's when I discovered the glory hole. I heard the person put some coins in and saw their booth light up from the video they were watching. THen I noticed a head go down to look at through the hole. I was nervous as hell for a moment, thinking I was about to get busted for indecent exposure. I covered up my dick for a moment. I then heard the unmistakable sounds of a guy masturbating coming from that booth. I figured, "aw what the hell," and started jerking off again as soon as I got hard. Whoever it was next door watched me until I came, then he zipped up and left.
It was very arousing to know I was being watched. I never repeated that episode although I thought about it for some time.