Initial Attraction: First of all, I am a humongous Harry Potter fanatic, so I am totally bias toward the book and would gladly watch 5 hour films that squeezed in every single Potter detail on every one of Rowling's pages.
The first thing that I missed right away was not seeing the emotional scene with Harry and Dudley where Dudley actually expresses his concern for Harry's safety and the Dursley's are shown to be taken to a safe place by goody wizard officials.
It was pretty epic to see Daniel Radcliffe in a bra though!
Another missing piece of the movie (literally) was George's ear. HE STILL HAD HIS EAR, his "holy" joke did not make sense at all...and no one even made a big deal about Hedwig or Mad Eye Moody's death.
The wedding party scene was good, but it was all over too fast and I missed Victor Krum being there. I didn't mind that Harry was himself and not disguised like in the book though.
I loved every second during the Ministry scenes, they were funny, interesting, exciting, and well executed. It was my favorite "part" or sequence of scenes in the Part 1 portion. Those Dementors scared the crap out of me!
All three of the main actors Daniel Radcliffe, Emma Watson, and Rupert Grint upped their game and gave really high quality performances. Watson's desperation in this scene shown above was particularly impressive and realistic and the blood was quite graphic for Harry Potter.
However, I didn't understand why Harry burst into another room which looked to be a child's room and why such a room would have existed in Bathilda's house. I felt that it was a lighting cheat so that we could see the scene and the snake better, but the entrance into this brightly colored room made the snake much less scary and easier to see, and therefore not as surprising and scary.
I also missed Voldemort arriving at Bathilda's house and Harry and Hermione's narrow escape, that part was so exciting in the book and it would have only taken a minute more of screen time to show it.
Another change or rather embellishment that I really loved was how EPIC the opening of the R.A.B. Horcrux locket was. All the faces and images that were in that massive, morphing cloud were gorgeous and the demon-esque Harry/ Hermione figures were very impressive (and may I say quite sexy when they were nude and kissing). Radcliffe and Watson apparently had their skin painted silver to achieve the look.
I wasn't pleased with Xenophilius Lovegood played by Rhys Ifans, he had the eccentric and awkwardness down, but he was missing his pleasant dreamy quality that is so like his daughter Luna (played to perfection even in her blip of screen time by Evanna Lynch).
The stinging jinx put on Harry gave props to the makeup department and I loved all the interaction at Malfoy Manor (again Watson was a standout). Ron wasn't nearly upset enough though when he and Harry were trapped in the cellar with Luna, Ollivander, and Griphook. Again, I cannot believe that the filmmakers just left Wormtail on the steps as if he had been knocked out, his death in the book is pivotal and incredibly moving.
Dobby's death was incredibly heartbreaking and the only scene which moved me to actual tears. The way they animated his ears made him incredibly pathetic and endearing like a sad puppy. I didn't like the way that Harry verbalized what he was feeling "I want to bury him and I don't want to use any magic" but I suppose that there is no way around it since there is no interior monologue going on.
The ending of the film was rather unsatisfying for me, I know that there is still so much ahead that will be epic, but I just felt underwhelmed, perhaps because the death of Dobby is so depressing and the film just leaves you hanging. It was very strange, it didn't feel like a Potter film.
Disappointments: Even split into two parts, I still don't feel like I saw a film that did justice to the book (even though I was promised that I would). I think that non-readers will be confused by this film, especially if they only view it once. I felt that it was a rather slow film that was punctuated by a lot of bursts of action.
Surprises: At the very start of Hermione's telling of "The Tale of the Three Brothers" I was lamenting the fact that it was animated, but the entire tale kept me riveted. Perhaps credit needs to be given to Rowling's incredible talent as a storyteller, but I remember whispering "Perfection" at the conclusion of the telling of the tale. The animation was bizarre, but incredibly beautiful and it fit in with the look of Potter.
Watch-ability: Don't get me wrong, I always enjoy a Potter film even if they don't squeeze in every detail. I think that we saw the best performance from every actor and actress on camera (especially the 3 principles). The film was beautifully shot and wonderfully executed, and the quality of the special effects is top notch. It is the darkest and most adult of the series so far, and definitely appropriate for a more mature audience as it should be.