This was super cute and fun! Robert Sean Leonard is very sweet and charming in the lead role and delivers some comic one-liners perfectly. (I just about lost it when he says 'The mirror's not working!')
It felt quite progressive in some ways for a movie from 1987. I thought it was cool that his parents, mistaking his odd behaviour due to vampirism for being gay, go do some research and are accepting of his being gay before they realise they're mistaken. It's also kind of refreshing (or, perhaps, a relief) for an 80s teen movie to not have any homophobic slurs bandied about.
It's campy, aesthetically pleasing, has Oingo Boingo on the soundtrack, a funny best friend who isn't annoying and a cute love interest with cool hair and great glasses. I loved it!
Although, the title is a little unfitting—I believe the original was 'I Was a Teenage Vampire' which is much better.