I finally finished it yesterday and can finally come out of the basement.
I thought it was good, despite 90% of the symbolism of the last scene going over my head. Just purely on a surface level, it's one of the most tense scenes I've ever sat through. I could see people wanting more closure but I agree with Sarah, everyone probably would've been more disappointed by a more straightforward ending. Paulie with the cat and A.J. giving up all of his new beliefs for a BMW was cool to see, among all the horrible bleakness. I was hoping they'd send it off with some humor.