The Prisoner of Azkaban is THE best Harry Potter movie. :) The new director/editor have put together a very emotional film full of suspense with none of the icky editing that bothered me so much in the first film. The first film had lots of sound and cutting errors so that the switches from scene to scene were not always flawless, and these little errors served to remind the audience that they were watching a film.
In this film there are no such reminders, and Buckbeak is so flawlessly melded in with the live action, that you really get a sense of being transported to another, more magical world. The magical sense of otherworldliness is fantastic, really well done.
Gary Oldman does a fine turn as Sirius, you really don't think of him as being Gary Oldman. A real chameleon, I wouldn't have known it was him if I hadn't read up on the production before I saw it.
David Thewles as Lupin, the werewolf dark arts teacher, does a great job with the many subtleties of the role. He is the first person to really give Harry bits of knowledge about his parents. There are several such moments, really touching.
Emma Thompson goes wild as the Divination Teacher who needs coke-bottle glasses to see. Some critics complained that she was overacting, but I think she just read the book and stuck with it. :) But then, I'm partial to Emma.
The new Dumbledore is an actor I like with a nice voice, and he does a more active Dumbledore which I liked because the books are always saying that even tho he looks old he never gives the impression of being aged, but this actor just doesn't bring the same sense of ... oh what's the word... gravitas? that Richard Harris did. A sense of gravity due to the seriousness of the situation, basically.
This film is darker than the first two (the Dementors are just as scary as they ought to be) and often often even funnier. The Whomping Willow for instance keeps whomping bluebirds and Buckbeak has fun chomping down on dead ferrets and flying bats.
Ron doesn't get a chance to do much in this film, but Hermione really comes into her own and Ron's twin brothers are sporting a "fab four" hairstyle. It's interesting to see how everyone is growing up. It's possible they might have to switch out the regular actors for younger actors, as they are all meant to be 13 in this film but none of them look as young as 13 anymore. I hope they keep the same actors for all the films, but you have to wonder! they're behind schedule as it is.