Zip is spot-on. I thought the movie was pretty good, but compared to the book, it went way too fast. Obviously, some fat is destined to get trimmed, as with the previous 4, but this particular installment is even leaner. Not surprising, it's a 870 page book in a little more than 2 hours. IMO, Order of the Phoenix is the best book so far, but it's not the best movie ("Prisoner of Azkaban" holds that honor). I felt, as I did with "Goblet of Fire", that if it just slowed down a slight bit, added maybe 20-30 minutes of time, it would have been much better and fuller, more rounded out.
So basically, it's still a great movie, but those who've read the book first will probably feel like I did that the story seemed rushed and a bit thin.\
A few points I feel like mentioning (spoiler alert):
Although probably not deliberate, you get some pretty heavy Darth Vader/Emperor and Obi Wan/Yoda overtones from Harry's teachers and enemies, and some Luke Skywalker overtones from Harry himself. This was all in the book of course, but when they boiled dozens of pages down into a few lines, it comes out sounding like Star Wars.
Michael Gambon continues his brasher, less kindly interpretation of Dumbledore, which works better in this installment (since Dumbledore purposely gives Harry the cold shoulder) than previous ones.
The Centaurs looked kinda cheesy. A bit disappointing. The rest of the graphics and special effects kicked ass.
There's absolutely no quidditch whatsoever in this film. One of the sacrifices made squeezing 870 pages into 2 hours of movie.
Alan Rickman as Professer Snape, as always, is awesome. One of my favorite things about the movies is that pretty much every character was perfectly cast (with the possible exception of Dumbledore Mk.2--Richard Harris was much better, alas, RIP) with exactly the right actors. But Alan Rickman as Snape takes the cake. Besides being one of the slickest villain actors of all time (Hans Gruber in "Die Hard), his greasy, snide line delivery matches the Snape in the books perfectly. If you read the books after seeing the movies, it's impossible not to imagine Alan Rickman giving Harry a bad time and playing favorites with his Slitherin students.