Harry Potter and the Shortest Movie of the Longest Book.

I went to the midnight showing of Harry Potter and the Order of the Phoenix last night/this morning. It is really hard for me to do anything but point out the differences between the movie and the book; I need some more time to think about it. What I can say from a movie-only POV is that the opening scenes were well done, the fight between Dumbledore and Voldemort was awesome, there was a disconnect in how Ginny, Luna and Neville knew about H.P. wanting to get to London, and hardly any of the teachers besides Umbridge (and maybe Snape) got any screen time. As far as omitting things from the book goes, I feel it could have used another 20 minutes (which would make it the same running time as Goblet of Fire, 158 minutes) to at least embellish things--particularly the conversation between Harry and Dumbledore at the end. Harry Potter and the Order of the Phoenix is 138 minutes long, and the book is 870 pages, compared to Harry Potter and the Sorcerer's Stone, which is 152 minutes long, and the book is 208 pages long. I mean, come on... fans of Harry Potter only come in one form--die hard. We would probably sit through a 4 hour movie. Why cheapen the story just to make it shorter than all previous movies?