I feel soooo oooooooollllddddd.
I remember standing in line one afternoon in Lubbock, Texas, in 1977 as a grown-ars* adult, waiting for the first movie. There was almost no advertising about it, but word of mouth was that you had to see it. For the "ooooh" factor when they jumped to light speed, if nothing else.
I still have the vinyl LP of the soundtrack bought shortly thereafter.