I liked the ending scene with Arya on the boat. It was beautifully shot, and looking at this while listening to the music helped with digesting all that went on during the episode. It was an intense finale, lots of stuff going on, lots of little tears running down my cheeks.
There will be a rewatch where details stand out more, but for now I'm not ready to think that Tyrion killed Shae in self-defense. While she did try to attack first, the violence on Tyrion's part looked to me like sheer desperation, humiliation, an bold emotional move. Shae, who he had tried to protect from death, was by now at her second treason. The way he said "I'm sorry" twice after the fact sold it for me, show-wise, that he fully intended to kill her no matter whether she grabbed the knife or not.
Not consequent to that but related, a TV show with so many villains/gray characters needs to have good people to keep the audience. Their good person was beheaded in S1, and there hasn't been any since. My thinking is that seeing how Dinklage became wildly popular, he was then their chosen anchor for this goal. They kind of did the same with Sansa, too, although Dinklage's charisma is by far the strongest one.