I remember watching it on late-night TV as a teenager...couldn't believe they were seriously trying to pass off the close-up shots of bunnies stumbling into scale models as terrifying.

I haven't seen it in years, since I was a teen too. I've thought of the movie much since encountering the feathered one.
Watching it again for the first time in ages, it was hilarious. Back then I didn't really follow actors and I didn't recognize Dr McCoy as being in it and I didn't see Psycho until I was 18 or 19 and had no idea who Janet Leigh was or that she was ever in actual good movies.
One of the funniest things was the pained reaction scenes, like when the sheriff looks at the first body covered in a red substance, though otherwise unmolested. Or when Janet Leigh's movie husband goes into the cave and he tells her to radio Dr McCoy and she has an over long pained reaction, lifts the radio to her mouth, and then lowers it again to extend the reaction of concern.
Or maybe she was thinking, as Janet Leigh, "Hey! I was killed by Psycho once. I am somebody! What am I doing in this horrible giant killer rabbit movie? I thought I was doing Harvey! *sob*"
I'm not sure if it was supposed to be an eco-disaster movie or a parody of an eco-disaster movie. The whole movie could have been avoided if one rancher would have just used poison and not gone looking to Science to solve all his problems. Science has it's own problems to worry about. And if it worries too much about your problems instead of its problems, we end up with giant killer mutant bunny rabbits.
Also, in some ways, it reminded me of Tremors, only without Kevin Bacon. And with a lot less competence. And a lot more giant killer mutant bunny rabbits.