Watched the third Harry Potter movie with Harti last night after going to Yvette's house, and... well...
To be entirely fair, here are ratings by category.
For a fan: 2/5
For a newbie: 3/5
Special Effects: 5/5
Quidditch: 0/5 (One tiny snippet so that Harry can fall off his broom)
Casting: 1/5
Soundtrack: 4/5
Comments: Heck to logic, let's focus on the pretty!

HP and the Prisoner of Azkaban, movie version, deviated quite a bit from the books. Case in point: First scene and first mistake, Harry uses light from his wand to study under the sheets. Hello, holiday=no magic by underage wizards? New magical invention not found in books: sarcastic shruken ghoul heads. All Hogwarts Professors have an uncanny liking for skulls and skeletons of weird creatures, and Lupin has candles that look like spinal cords (I swear the vertebrate are labelled. I even saw the Roman numerals). Then they made Ron more stupid than usual, and swapped lines around. Plus, they made Lupin sound like he was in love with Lily, and Dumbledore sprout weird poetic musings.
Even if the movie was taken as a (very) loose adaptation of PoA, there were some odd ends that only could be tied up by reading the book. Lupin uses Immobilus to stop the tree from moving, but people who don't know Latin/book incantations by heart will have no idea why the tree stopped. And the lighting! One minute Harry is talking to Snape in a pitch-dark corridor, and when he gets rescued by Lupin he is lectured in a morning light classroom.
The Hogwarts grounds have changed completely, with Hagrid's hut closer to the school and the lake beyond the Forbidden Forest. Plus, where did all those Stonehedge rocks come from? That having been said, the grounds still look lovely. Perhaps it's closer to the moorland that I imagined Hogwarts to surrounded by, that's why. The Great Hall suddenly has a clock tower, but the clock looks nice so I forgive them. Anyway, time plays a great part in the story. The Infirmary being in the clock tower sounds ridiculous to me. How do the patients sleep? Hogsmeade looks gorgeous, I'd like to go there.
Special effects were the best! Buckbeak looks so realistic and lovely I want a Hippogriff. The Dementors moved realistically, down to the way everything turned to ice around them and how their rags fluttered. Portraits were as lively as usual, with a taller-than-expected Sir Cadogan. The werewolf and big black dog were savage and moved in a convincing loping manner. There were also shooting stars on the ceiling of the Great Hall, a nice touch. The director has a flair for nice shots.
But not for coherent plots! Or for choosing actors!
Lupin: Moustache. Taller than Sirius. More stern than kind. More bitter than tired. MAN, DIDN'T YOU READ THE BOOKS!
Sirius: Very gay. I swear if I didn't know better I'd thought he was a girl.
Peter: I think it's impossible for any human to look like that. When I first saw him I thought of a very dirty White Rabbit in Alice in Wonderland, given how fat he was and how he kept running away. I half-expected him to go "I'm late! I'm late!" at some points in time.
But I'm nitpicking. Right now I'm listening to the lovely soundtrack (courtesy of Jane, arigato!). What's the quality like? A sample is Double Trouble by the 'Hogwarts Choir' in the movie, an enjoyable and lively piece. Listen to the movie and watch the nice effects, even if you have to leave your brain at home.