I remember seeing Jurassic Park in the theatre a couple of days before its official release. A friend of mine worked at a theatre (which was brand new and had all the latest bells and whistles for the time) and was able to bring a guest to the employee advanced showing. Since we were both big-time movie buffs (and huge Spielberg fans), I was his natural (and usual) choice. Even more impressive than the visuals, was the sound.
The trailers started up, and since over half the audience were theatre employees, they weren't paying any attention. They had all seen them all a hundred times, and kept talking, so I could barely hear the trailers' soundtracks over the buzz of the crowd. I said to my buddy, "Shouldn't they turn up the volume for the show?" He said, "Just wait, this movie has one of the first digital soundtracks (which meant nothing to me). It'll be plenty loud." Boy, was he right. The trailers all had analogue sound and the volume difference alone, was impressive. Never mind the quality of that sound. All in all, a technological tour de force.