Well, about 25 minutes into ep3 me and my wife stopped taking it seriously. By the end we were openly mocking it. There just isn't much that works with this episode, not even on the levels that a GoT episode usually does. The darkness is the obvious culprit, as are the many weird cuts of showing close ups of people running or fighting in the same darkness, so that you never get a chance to see what's happening. The actual plot developments are pretty thin and relegated to pretty much four characters (Melisandre closes her arc, Arya gets yet another thing to do and Sansa and Tyrion are maybe sort of in love, I guess?) but the spectacle is so badly done. The tactics are so obviously moronic that the "it is cinematic" excuse doesn't work, especially not when episode then can't decide how far or near the white walkers are. Some guys try to put torches to the tar-filled moot but white walkers cut them down, so Mel casually walks up while a few Unsullied strike power poses around her and suddenly there are no white walkers between the moot and the wall, instead they are all hundreds of meters away and rushing up (despite having just pushed out the Unsullied from their position forward of the moot) so that Mel can get a tense moment of having to use her magic.
Then the white walkers somehow manages to climb the walls and are in the castle and suddenly there are Schroedinger's zombies everywhere. People fight on the walls, in the courtyards and in the side passages. But Arya is in the library and despite the fight going on outside, the white walkers in the library decide to casually stroll around so that Arya can do her Solid Snake routine. At this point, and I'm not kidding, my wife said "this is a video game" and the sudden shift from battle and massive stakes to "Arya slips around a bunch of book cases" was so jarring that I never felt that the pace of the episode recovered.
Somewhere around here there's a really cool dragon fight scene. I'll give the episode that the shots of the dragons fighting were cool. But then we're back to the ground and Beric dies (I am sure a lot of people didn't see that coming) so Arya and the Hound can run. Mel shows up with them and tells Arya that she's the chosen one and has her set off to kill the Night King. So off Arya runs for 30 minutes. Meanwhile everyone is losing the fight! And then they lose the fight! And then they lose even more! And then they lose even harder. Now, I realize that the scenes around the time NK stands up Johnny to go hang with his step-brother and up to the point NK comes to party with the Raven is probably only between 5 to 10 minutes. I realize this, but since the episode has been showing us how everyone is on the last leg for the last 15 minutes, it just murders the pacing (again) to show us how they are now losing even harder. At this point the show is pretty much vesting all hopes in the music to carry the tension, because the sheer length of time that everything is hanging precariously in the balance is so drawn out that it induces apathy.
Theon decides to be a moron and die because Bran calls him a good guy, in case any viewer out there hasn't understood that Theon's arc was about his realization that he was born a Greyjoy but raised a Stark and that he had betrayed the people he thought of as family. Bran spells it out so that you don't have to think about nuance and Theon dies. Then Arya teleports in, shanks the Night King and BAM! the overarching plot of all of GoT is resolved with a kidney stabbing. Meanwhile, Jon, the guy who has been fighting the NK's goons for the last 6 seasons, gets to shout at NKs pet undead dragon, because it'd be a shame if Jon's arc actually got a satisfactory ending when we can prop up psycho-killer Arya some more. Also the annoying ten year old Lady Mormont gets crushed by a giant and I was happy that I won't have to see yet another scene with her fucking up the theme of "medieval patriarchy is awful" by being a flagrant middle finger to Martin's actual writing.
With that recap over, I've got to say I'm disappointed. I thought that ep 2 was one of the best episodes of the last 3 seasons, even as it stumbled it still managed to tie up a lot of character work neatly. We got to see people react to each other and handle their fear and despair in different ways and it was actually pretty strong writing (mostly) backed-up by the usual top notch acting from most of the cast. Ep 3 is, without a doubt, the worst episode of GoT I've ever seen. As a climax it drags on for way too long, it does little with the characters except put them in danger (and then fails to deliver any but the most obvious deaths) and the actual ending is not shocking when you consider D&Ds raging hard-ons for "surprises" and the character of Arya, but is still a massive let down if you look at it dramathurgically.
As others have said, the big threat that's been foreshadowed since season 1 is killed off before mid-season in one episode. Left is the pretty inconsequential struggle for the Iron Throne (because it is not like Dany can just head back to Mereen or anyth- oh wait). It also feels as if the showrunners simply didn't know what to do with the white walkers. There's easily half a season worth of content that can be made from the attempts to slow them down prior to reaching Winterfell, so that proper defenses can be prepared. Not only would that have played up how dangerous the WWs are, it would have allowed for more organic threat escalation ("The wildling trap failed, the road to Winterfell is open", "I'll march the Unsullied out to delay for as long as we can!") and for the actual confrontation with the NK to be something more than just the thing that allows us to stop feeling the ending fatigue of a badly paced battle episode. To have the entire showdown with the WWs amount to one badly paced episode is a gross mishandling of the big bad of the entire show, especially when said big bad is killed off before the silly secondary threat of Pervert Jack Spa- Euron Greyjoy.
I know the show isn't over yet, but I'll consider myself proven right in my prediction that D&D would be utterly unable to actually bring GoT to a satisfying conclusion. Because they just removed the big bad prior to the mid-season episode in the silliest fashion possible (well, I suppose Sam stumble killing the NK with some sharpened dragonglass would have been sillier, but not by much).