Caught this last night for the first time.
Agree with the OP; no part of this movie works, but somehow the movie as a whole works. I kept thinking during it that it ought to be either a lot funnier or a lot scarier, and I was conscious of being disappointed with it as I watched it, but at some point it won me over. I think part of the good feeling it leaves you with comes from the (spoilers ahead) fakeout killing of one of the leads. When they give her an unexpected reprieve it earns the movie a lot of goodwill and positive momentum heading into the nice ending (which again ends on an unexpected positive note).
That said, it's bizarre for a cult film in that it's so quiet and modest and slow, and character-driven. Almost a meditative b-movie. And it really is super-slow and nothing-y for much of its runtime, to a degree difficult to describe. There's really no attempt to create any tension or conflict for the first hour or so. Of a 90 minute movie.
Also I loved the male and female leads in this, the girl especially. My first thought after watching it was that she'd have made a perfect Lois Lane.