I agree that it is one of the best shows on television.
I just think there are some viewers who were really turned off by the events of last night. Good storytelling manipulates the reader/viewer just right and orchestrates events to alternately surprise, shock, intrigue and satisfy the audience. There needs to be just the right balance. We like to see a good payoff to a storyline we've been following. This was not the payoff some viewers wanted, and if a show goes too far in denying the audience what they want to see, the audience will revolt.
Last night pushed some people right up to the edge, and a few others went right over and are having an emotional response of hatred towards the show and author. They feel abused and betrayed and think the show broke the promise of a happy ending that realistically wasn't there to begin with. We allow ourselves to be emotionally manipulated by a story with the implicit understanding that the storyteller will give us a satisfying and happy ending. We expect it to be a safe and ultimately predictable experience. (We like twists and turns along the way, but in the end the guy needs to get the girl and the good guy always wins.) It turns out GoT isn't that kind of story--and you could certainly argue that viewers should have figured that out by now.