Ok. I just got back from seeing it a couple of hours ago, and I'm not impressed. At first the special effects and whatnot make it seem really good, but the more I think about it, the more things I can think of that deviate from the book when they really didn't have to. Excuse the following rant.
What was completely fucked
I absolutely hated Hermione and Dumbledore. Dumbledore was way too violent in pushing Harry and he yelled too much. In one scene when he and Harry were in his office, Dumbledore kept moving around, and then jumped onto the staircase and sat down... in the books he seems really composed and assured, in movies 3 and 4 he seems like a violent old man with a weird accent and a yellowing ponytail for a beard.
Hermione was a whiny little bitch. WTF at the psycho she had at Ron after the Yule Ball. Her voice is so annoying! I really think they should have done more to make it seem like a bigger transformation when we see her at the Yule Ball. She's too pretty ordinarily. Bring back the bushy hair!
I was also uncomfortable during the Durmstrang and Beauxbatons' entrances, how they did their little performances, it just seemed out of place. I also imagined that both schools were co-ed.
Sirius in the fire... don't even get me started. Blasphemy!
Oh, and when Harry was looking for Cedric in that courtyard thing to tell him about the dragons for the first task, and everyone was mocking Harry with those "Potter Stinks" badges, they focused on a girl with blonde hair (I THINK, it happened really quickly). Did anyone think this might be Luna Lovegood?
I really didn't like the hedge action in the third task. I was expecting to see the sphinx's riddle, the large spider attack Cedric, etc., but instead we see the hedges collapsing, and people 'changing' (as DD said before they entered)?
DEATH EATER KKK HOODS = no no no! That was stupid. Also, why did they make it so Barty Crouch Jr. cast Morsmordre after the DE attacks had died down? I thought when he cast the Dark Mark in the book it was to scare the Death Eaters (i.e. Voldemort's betrayers cause they were doing nothing to bring him back)?
I hated the fight between Harry and Ron. Ron seemed like such a pussy; in the book he won't even speak to Harry let alone help him with the first task! Did anyone cringe when after they made up Hermione was like "BOYS LOL!!!11"
It also jumped around really quickly from scene to scene. I know that it's hard to condense such a detailed book into less than 3 hours, but for people who haven't read the book it's gonna be hard to understand what the hell is going on.
What I liked
I liked Cho Chang's Scottish accent, although I heard a fair few people around me going WTF is wrong with her voice
The egg was great. I liked the song (although I DIDN'T like the Harry/Murtle action they had going on!) I also liked how Harry transformed after he ate the Gillyweed. The flip was pretty cool.
I liked how they incorporated Moody's swigs of Polyjuice right throughout the movie, making a first timer think he was an drunk. I also thought Draco's ferret transfiguration was well done, although when he crawled down Goyle/Crabbe's(? I can't remember) pants, it was a bit suss :S
Cedric's death = good. I'll admit it. I cried. When Harry portkeyed out of the graveyard and returned, and the upbeat music started and everyone started cheering, but Harry was just lying over Cedric's body not letting go, and then Fleur screamed, and then Amos Diggory started screaming "That's my boy!".. omg. I couldn't help it. I'm pathetic.
I'll probably think of more things later.