Joss Whedon wrote the script, but he hated what they did with it, so he walked off the set and never came back. See, Whedon wanted the movie to be a bit more serious than the producers were envisioning it. His disappointment led him to create Buffy the Vampire Slayer (1997) which remained on TV for seven years.
Here's my review for the movie: it was absolutely ridiculous. The vampires looked stupid; the fight scenes were laughable; the story moved too quickly; and the acting was pretty bad. I saw a review that said it was the 80s movie of the 90s and it basically was. Maybe if I wasn't almost all the way through Buffy the series, I would have liked it better, but I doubt it. It seemed like a pretty low budget movie--especially considering the television series had better effects in it. I mean, the vampires didn't even dust! How boring!
Another complaint I had against it was the length and timing. In a 40 minute episode, Buffy not only saves the world, but is able to make a speech about something or other, go to school, slay a vamp or two (while making clever little quips), and go on a date with whatever guy (undead or no) she might be dating at the time. It took 86 minutes for the movie to do that, but the timing was so off! It took too long for her to learn she was the slayer, and then all the fights were way too short, and the climax came and went almost without me realizing it. So in some ways it was too long and in others it was too short.
I can see how Joss would be disappointed. Everything else I have ever seen done by him has been witty, but serious, with great character development and clever use of cinematography. And I'm glad that he took it upon himself to right that wrong by creating the series because I have been enjoying it immensely.
So, I wouldn't recommend Buffy (1992) to anyone. If you want some serious and fun vampire butt kicking, watch the series instead.