Are we ok with posting book/movie 7 spoilers in this thread? If you don't want them then don't read my post as it's hard to discuss my major issues with the movie (plot holes leading into the the next movies)
I think you misunderstood the ending then. It wasn't like the book with the kickass battle, but it did make sense. Voldemort wants Dumbledore dead, supposedly by Draco. He knows Draco won't be able to do it, so he makes the Death Eaters go along to make sure he is still killed. Once he is dead, their job there is done, and there is no remaining "real" threat to them at Hogwarts for when they return later. They don't peacefully leave either, they (Bella especially) celebrate like crazy, running through the buildings destroying things, shooting off the Dark Mark, fleeing through the grounds and destroying Hagrid's house on the way out. Throughout the whole movie they were destroying things and not sticking around either.
I didn't like how they cut out the battle, Dumbledore's funeral (where he is buried with his WAND), cut out the Gaunts memory, or put any emphasis on the ring, or even MENTION the (real) locket. The book also had about 4 plotlines going on, and of all of them, the one they emphasize was the retarded romance! They didn't even get it right, Harry didn't know about Hermione's crush and Harry was supposed to officially be with Ginny. How else is he supposed to dump her for the next movie? We also miss out on meeting Bill, EVER, but supposedly the wedding is still on for the next movie. That'll take up some precious screen time to introduce.
You didn't like Ginny, but I thought she was fine. Harry bugged the shit out of me though, every time he tries to laugh it's just creepy. See: making fun of Dumbledore's age, or when they're in the hallway watching the younguns find their classes. Maybe he's just weird looking but it was disturbing to me.
In all I guess I have to accept that it's a movie adaptation BASED on a book, but I'm still curious to see how they'll cover their ass on some things. I did enjoy myself while watching though, don't get me wrong.(DUMBLEDORE FIRESTORM HOLY SHIT)