The movie itself, amazingly, seems better than ever. It's astonishing to watch it afresh and realize how, to this day, each new comedy steals liberally from it. It's not an especially good looking movie—the Blu-ray transfer doesn't reveal anything except how dark a lot of the picture looks much of the time. Shot in Eugene with the University of Oregon campus subbing for a fictional Pennsylvania college, it's interesting to see a bit more clearly how rainy and wet the shoot was, and you can see some Oregon mountains in the background of the ROTC scene which I'd never noticed. You can also see a rat running along the stairs behind John Belushi in a scene right before they sneak into the dean's office.
None of these are reasons to upgrade to Blu-ray.
As for the special features, they're negligible. There isn't commentary, but there is a little pop-up video track with talking heads that accompanies about 40-50% of the movie's runtime. Some of this video is plucked straight out of the accompanying documentary, which itself is so-so, and obviously left over from a previous DVD release. I suppose it's worthwhile viewing, especially since all accounts remember that the film seemed doomed from the start, so its subsequently huge success was highly improbable. It's also interesting to realize that the guy who played D-Day is, hey, that guy! I recognize that guy! And there's also ample proof, if you need it, that in real life Kevin Bacon is a douchey spazz.
Other features are a trivia game which I found surprisingly hard (Animal House is not the kind of movie that inspires studious, careful viewing), and there is one special feature that is so terrible that I urge you never to ever, ever select it on the menu: It's an update on the film's characters taken directly out of the charming "Where Are They Now?" captions at the film's close. So yes, we see old Peter Riegart and old Karen Allen in the year 2003, oldly looking old and still arguing over nothing; we see a surprisingly svelte Flounder sitting behind some desk; we see that blonde girl as a Universal Studios tour guide; we see a dazed Otis Day pretending not to be Otis Day. It takes those great suggestive captions and creates a literal film version of them. (For obvious reasons, they don't include Belushi's Senator Blutarsky.) It's awful. Don't watch it.
So in summation, the Blu-ray edition of Animal House is adequate, nothing more. It's not worth upgrading from your DVD edition. Hell, it's probably not even worth upgrading from the old, battered VHS that you inherited by being the last one to move out of your shared house after college. If you somehow don't already own this movie: fine, go for it. Otherwise, skip it.