I am one of those people who loved this movie as a kid but for me it still holds up to this day. It's not a perfect movie by any accounts, the animation swings between gorgeous and fluid and ugy and jittery at points, but is overall nice. The songs are good and unobtrusive, and aren't presented like a typical mysical, perhaps minus the one where the characters sing in the story itself. The plot is somewhat bare, stripped down from the deeper plot of the book, but its servicable for a kids move.
There are some darker parts to this movie that I think are pretty typical for films that came out in this time period. There are a few soft curse words and some parts that might scare smaller kids. The violence isn't graphic but it's not presented gently either, and there is some 'nudity'. I put that in quotes because you briefly see part of breasts on a monster character. It's not in the least bit sexual and I didn't even notice they were there until I was an adult. It's not something I think kids would even really notice, as they're mostly obscured and the movie doesn't put any particular emphasis on them.
One great thing about this movie is that you don't have to worry about there being potty humor and fart jokes every five seconds like there is in so many kids films today and there is what feels like real danger and scares as well as real beauty in the film. It's not for everyone but it's a wonderful movie that's well worth a try.