One thing that I've noticed is this movie is better the 2nd time. The first time you're sort of surprised at how inactive the movie is.
My advice to first timers: read the novelization first. It's a brisk read, fills in soooooooo many gaps and is probably the fluke that made me love ST:TMP so much in December 1979, going into it otherwise knowing only a few random TOS and TAS episodes.