I was almost disappointed. I thought it would be SPECTACULAR and it was merely Good. However, the sight of Snape in drag was worth the price of admission alone. 
I am in agreement that it was way too fast-paced. I know you have a lot of ground to cover and you don’t want the kiddies getting bored, but the movie ran about 2:20 and you could have put in an extra ten minutes’ worth of film and dialogue with no harm to the running time. I felt the Aunt Marge and Knight Bus scenes spent a little too much time on business, belaboring the “she’s getting bigger…and bigger” like something out of Monty Python, and the “look at the funny bus squeezing between the other buses” stuff, and then speeding up from Harry’s arrival at the inn onwards.
You have a large ensemble of talented, appealing character actors who are allowed to deliver their lines and perform their bits of business in one or two scenes before the movie races away to the next scene. A number of scenes are meant to be powerful emotional moments for Harry: when Harry thinks he’s going to be expelled for using magic on Aunt Marge; the adults’ conversation in Hogsmeade about Sirius’s history with James; of course the whole Shrieking Shack scene; even the destruction of Harry’s broom – in the book, he’s devastated by this.
The Shrieking Shack scene is a very talky four chapters in the book, IIRC, and I wasn’t expecting to hear all of it. But this is a pivotal scene in which we have to get from “Sirius Black is a violent lunatic out to kill Harry” to “Sirius Black is a much-loved, loyal friend of the Potters’ who was cruelly betrayed and unjustly sent to prison.” By the end of it, Harry is thrilled by the possibility of going to live with his godfather. There is also the business of Lupin apparently switching sides when he embraces Sirius – not only is there the horrified, “I don’t believe this!” moment for the kids, but the realization that Lupin himself didn’t know the truth about his old friend all this time. David Thewlis has played a lot of bad guys, probably because of the way he looks; here again we get the possibility that, like Professor Quirrell, a trusted adult turns out to be a bad guy. Lupin helps pull us over to the understanding that this frightening stranger is really just a dear friend in trouble.
I think there’s a rule in adapting screenplays from other sources that you should never lose the big lines, the ones that everyone is expecting to hear. As someone else already mentioned, they lost Ron’s "I let you sleep in my bed!" line, which is priceless in its combination of horror and comedy. I was also waiting for Harry’s line, “This is the weirdest thing we’ve ever done,” as he and Hermione watch themselves near Hagrid’s hut. I thought that would have been a good laugh line.
Other stuff:
Hogwarts is absolutely gorgeous. Stunning. The grounds, the moving paintings, that suspended bridge, the classrooms, the (perceived) use of natural light. Wow. I would be awed and humbled to attend such a school.
Emma Watson was great. At the risk of sounding “pervy” myself, that Rupert Grint is growing up to be a nice-looking young man. Daniel Radcliffe is fine and appealing, but I agree that his big emotional scene in the snow was lame. I also thought the scene where he finally uses the Patronus Charm successfully to be weak – that’s the kind of thing that should have me in tears, and I wasn’t.
Lupin’s mustache threw me – I thought it looked too 1930s, when the rest of the school is, well, 1730s.
When Harry threw his arms out while riding Buckbeak, I thought of The Black Stallion instead of Titanic.
Sirius in animal form should be a big, powerful, beautiful Newfoundland, not a skinny black wolf.
I really liked the moment when Sirius grabs Lupin as he’s changing and tries to talk him down. That wasn’t in the book. “Remember who you are…you’re in your heart” or whatever it was – even if it suggests that being a werewolf is controllable, it shows the intense friendship of these two men who haven’t seen each other in years, and Sirius’ devotion to the people dear to him.
Question: the business about seeing Peter Pettigrew’s name on the Map wasn’t in the book, was it? They may be trying to prepare us for the Bartemious Crouch business coming up.