"Why does a stupid cut suddenly rip itself into her leg?"
That's from the holy water they're throwing at her. I kinda know what you mean- some of that stuff does lose its edge with repeat viewings but I maintain that the film still manages to unnerve and also has other things to offer (like the bleak dimly-lit almost grimy atmosphere you mentioned). Also, I'm sure we've discussed this but I own "the version you've never seen" and prefer that one. Of course I grew up on the original but when I saw the newer version when it was first assembled and released in theaters in '00, it made me appreciate the film more. That version also has more of that subliminal stuff you're talking about.
"And the biggest jump in the movie comes from the phone ringing too loudly when Karras is listening to Regan's tapes."
You pussy. Actually, I remember the first time I saw it, in addition to being disturbed by all the infamous shock moments, I was also really freaked out by the scene where Regan's involuntarily flipping back and forth on the bed