I have now seen DHII Twice (in 3D, no less)
The second time, I was with 2 adults who have not followed the books or the film series, and they were totally lost. The film cannot stand alone. But then, I never expected it could. It's a series for a reason.
The film moves quite briskly, until the Final Battle, where we spend far too much time staring at rubble and people doing nothing significant.
And where did the producers think that the Wizarding World would come up with so many Death Eaters, when the entire Wizarding population of Britain was set at 5000 men, women and children? That was one cinematic effect that works against the canon. There were no Inferi to boost the numbers that I could identify.
I have to admire the 3D effects. This is the first 3D film I've seen that makes good use of the technology. I especially liked the stone statues coming to life to defend the castle...I agree with McGonagall about the delight of using that particular spell--and Molly's side glance of disbelief is precious. Molly's duel with Bellatrix is as contrived in the film as it was in the book, but it is mercifully brief.
The screen writers did a fabulous job editing the trash pile that the last book was into a tale with beginning, middle, end, continuity (as much as possible), etc. Every scene change deleted a half a chapter, at least, and half a dozen limp and excessive plot twists. But the most masterful job was the repair and reconstruction of Snape's tale.
With the elimination of Snape's parental issues, never well-defined, and Lily's cruelty, never acknowledged, we see how a man can devote himself to a life task (leben) and a dead woman (lieben), and not regret dying after completing his task.
The irony that Snape is the final sacrifice, when he and Albus both thought Harry was, is galling. But at least it is coherent, and therefore bearable. I do wish the snark "Would you like me to do it now, or after you have composed a suitable epitaph?" had been left in....the airbrushing of Snape's features to erase the years was not particularly convincing, since his jaw line was never tightened.
I say again, Well done, Screen Writers! And for shame, publishers, for letting a book go out half-dressed and all higglety-pigglety.
And there's STILL nothing to prevent a Severus Snape rescue, rehab and revival, preferably with the horrors of his past removed to a distance.
And think of poor Albus Severus! With his trunk clearly labelled ASP, what chance has he of surviving in any House save Slytherin? Nice aging of the Trio--they don't look 40, but they look old enough to have kids in Hogwarts. 8 years was always far too long for them to put off families, anyway.