When I review for parents, I count the profanity by # words -- I never saw Grindhouse, which probably had the most recently, but my top F-word find was Pineapple Express with 170 and plenty other profanity. But, PE was the only film with so much profanity that it was funny to me. The worst profanity usually leaves an extremly literal bad taste in my mouth and I walk out, and PE dialogue is the only one that did not.
To spend $$$$ on a film with the worst profanity, though, I won't do it. It's a waste of money. F-words and sexual profanity are abuse to me and almost all abuse starts with verbal abuse. I won't pay for it and won't allow it in my personal life. It's not art and in rap music, usually misogynist as well. F-words also mean a lack of vocabulary and thinking. If a PG-13 film has 1 F-word, I won't scream; they're allowed 3 and I've heard it before. During 9/11 tragedies, people literally had nothing left to say, so that's understandable. But one PG-13 film recently included 7 F-words and the studio tried to say it did not, because a few were in a loud, clear rap song. "It didn't count," they say. That's a lie.
As PG-13 slips past the 3-limit, R's will have hundreds more in future. At least I don't have to pay money for it when I review.