Definitely the best of the three. The previous two, unfortunately, were very close to the book in some regards, and thus suffered badly as movies. This one worked well as a movie--a little rushed, as one might expect, but no "Why the hell did they leave this scene in, when they cut all the bits that it was attached to?" as happened in the previous ones. It was not slavishly faithful to the book, and thus spared us a lot of unneccessary Quidditch, for which we must all be grateful.
We will undoubtedly see a flood of hippogriff fan art, so everybody get out your waders.
Lots of people whined about the werewolf design. I rather liked it. Werewolves have gotten all popular and hip and so on, and thus the standard portrayal is a big, noble, anthro-wolf, usually with dreamcatcher earrings. So I was pleased to see a werewolf that was an actual combination of human and wolf, and about as ugly and lanky and spindly and ungainly as one might expect from combining the two--the whole point of werewolves in the HP universe is that you DON'T want to be one, it's a curse, you're a ravening madman, and if they looked all shaggy and noble and decked out in tribal finery and were polite, meh, some curse. It's nice to see.
Good dementor design. Given what they had to work with, looked as far from being a Nazgul as a big black hooded wraith can avoid looking like another big black hooded wraith--i.e. not very, but they made a good effort.
My favorite bit, oddly enough, came during the werewolf attack, and was simply that when Snape is confronted by the werewolf, the first thing he does is try to shield the three kids with his body. I mean, they're three whiny little bastards that he loathes with an undying passion, one just attacked him--and nevertheless, his first act is, quite properly, to act like a professor and much more experienced wizard, and fling himself over the inept. It's a nice touch. I like Snape quite a lot, mind you, mostly because I'm so bloody sick of Harry whining in the books, and while it was an understated, corner-of-the-eye kind of thing, I thought it was very nicely done and saved him from being a straightforward bastard throughout the flick.
In other news, while at the bookstore, I wandered over to see if "Wolves of the Calla" was out in paperback yet, only to discover, to my horror, that the NEXT Dark Tower book is out already. Shit. While I'm glad they're putting them out so that the series will actually be done before King dies, it certainly made me feel out of the loop...but hey, such is life. I'll find it used eventually...