This is a true Detective Spoiler thread, so it will be beneath the fold.
I think the most satisfying portion of the show was the arc and the closure we had tonight. For me, what mattered was the closing discussion, after it was all over, and both of them had come to their own peace. Obviously Rust Cohle still had his demons that he will always have, but for me the closing scene was about two people coming to terms and becoming one. Becoming True Detectives and True Partners.
Remember, earlier in the season, any time that Rust would speak openly, it made Hart feel uncomfortable. There was the atheistic/nihilistic scene in the car where Rust spoke about the philosophical underpinnings of his existence, in which his whole belief that humans were just an aberration and that we had grown consciousness beyond our understanding, and Hart was upset he had tried to get him to open up and declared the car (and I think I am getting this right) a “place of quiet reflection.”
Then, tonight, we watch Hart start to think like Rust- it was Hart who put the green ears on the man with the scars together with the picture of the green house. That was something his character would not have been able to intuit in the earlier episodes when he was a younger man. But as he and the show progressed, he and Rust became more and more alike. They went from different, disparate individuals, went through their own progression through life over a few decades, and they changed.
And what we saw at the end was the end of the arc. They had both changed, and the scene that ended the series said it all. Whereas before, Hart would have never listened to Rust talk that way in the past, this time, not only did he sit and listen, but he understood, because the bond had been formed and they had become one. A team. True Detectives.
And that is my take. Just a beautiful, intricately layered, brilliantly written show, and what is so amazing is that all the clues were there, but the dialogue and acting were so good we missed the signs and clues. This show will serve as a writing and acting clinic for decades to come.
There is just such a perfect sense of completion with this finale. This story was never about the murders. It was about the journey of Hart and Cohle.
*** Update ***
Now that I have distilled my thoughts, let me put it more succinctly. In my opinion, the entire show was an elaborate misdirection. We were completely distracted by the exquisite dialog, the imagery, the gruesomeness of the murders and the gothic intrigue, and we spent eight episodes trying to figure out who the murderer was and what clues we had missed. But that was all a ruse, and what we were supposed to take from the show was the relationship between Hart and Cohle. We missed the story they were telling while looking for the clues to a murder mystery.