I don't get what the big deal is with the Jamie/Cersei thing (as a non-book reader). He's been battered, imprisoned, and emasculated for years (in RL time; not sure how long the Starks had him in their timeline), and even when he finally gets back home, he does so missing a hand, his position is mocked by the king and the hand and his professional life seems to be over, and his illicit sister/lover has the nerve to reject him and then ask him to kill their brother for doing something that they both probably realize he didn't do and which they both know was for the best anyway.
Not that what he did to her was a good thing, but there was an abundance of reason for him to do it. Him finally taking out his pent-up anger and frustration seemed in-character to me. I can't say I ever bought him as being redemptive in the first place. And, as one writer noted, if he had just taken a sword and impaled Cersei, people would have cheered her death almost as hard as they did the death of her son. I don't get why this whole thing has become a news story.
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On an unrelated note, Oberyn is killing it. He's only been in a few scenes but his presence is so powerful you wouldn't know it. His confrontation with the de facto king was priceless. The stuff at the end of the show seemed a little silly to me with the horseman making a fool out of himself and the good ol' magical voice enhancement kicking in so people a mile away can hear a smallish woman speaking. But the titular gag at the end was pretty good.