I think this was also a group of mainly non-book readers, because there was a general murmur of surprise during the Pensieve scene and several gasps at '19 Years Later'. I'm kind of jealous of that group, well, for the same reason I'm kind of jealous of the people who watched Game of Thrones before reading it and didn't know exactly what was coming by the end of the season.
In general... I enjoyed this movie as a whole a lot, for many of the same reasons that I enjoyed the book. But I kind of want to have this movie's babies from Snape's death onward (even though the final final battle was probably a bit more drawn out than it had to be). Oddly enough, that's the place in the book when - during my first reading - the waterworks started.
There's a long and storied tradition of, as my cousin put it as a little kid, the bad guy in a book or movie "getting nice at the end". Snape was always the guy you loved to hate, and he didn't so much get nice at the end as you suddenly realized that, although he was pretty much a dickweed to Harry, he had his reasons, and he wasn't a bad guy after all, and shame on you for thinking he was. I don't know what the general consensus is, and I'm sure there are plenty of critics, but I thought Alan Rickman was amazing. It was startling to see Snape showing actual emotions (other than disgust, loathing, etc) but it never felt out of character or that he was chewing the scenery *cough*Gary*cough* By the end of the series I kinda wanted to hug him... didn't see that coming.
I'm bummed at how little Remus and Tonks were in both of the movies - how many of those non-readers in the theater today went 'Huh? He has a son?' during the Resurrection Stone scene - and I don't think it would have taken too much screen time to rectify that.
But, my own ship grumps aside, the screenplay was put together well. The exposition was pretty much kept to the first few scenes in the cottage and after that there was a brisk, fairly constant pace that kept everything moving. And the technicalities of wand possession made sense, IMO, and that's coming from someone who had to go back and reread sections of the book in order to follow the whole Grindlewald->Dumbeldore->Draco-not-Snape-
Me: No, Harry! Don't snap the Elder Wand! You haven't fixed your own wand yet, you-- oh, well, okay, I'll just assume you did that off-camera then. :-\
So, the epilogue. I'll be honest, while it reads a little like fanfic, I kind of love it. I would have indulged in the same way if I were JKR. I think the way it was portrayed in the movie is an improvement because it was condensed, and honestly? I couldn't stop staring at 36-year-old-Harry, and I couldn't help but have a warm fuzzy feeling at the fade-to-black. Because they're married! With cute little wizard kids! !!!!!!!!
- Neville. I luff you. Especially now that you're hot.
- Draco: LOL U R a douche and you know it.
- Percy: Your redemption was off-screen... sucks for you!
- Lav: Did she die? Do I care? Not really.