The special effects department went through 25 gallons of fake blood during the shoot.
I watched it knowing in advance that I would always like Lovecraft's short story better. The first striking thing about the movie was the score, which was basically Bernard Herrmann's Psycho theme. It was pretty annoying to hear a classic theme passed off as something original. Underneath the added stuff, it still holds the Pyscho charm. (UPDATE: Having watched the making of Re-Animator, the score doesn't bother me at all. It was acknowledged that it was a tribute to Herrmann's theme.)
I've warmed to it after 2 more viewings... Obviously; if I didn't like it, I wouldn't have watched it again. Twice.
I was also lucky enough to get the DVD edition with a fabulous green marker in the shape of a syringe!