I'm glad they at least made Snape back up to be someone we could...you know...hate instead of laugh at like GoF. Hands down, best portrayal of the movie has to go to Umbridge. Granted, the character has a built in hate-factor (arguably one of the best written HP villains considering she only got one book to work her bad on) but she was portrayed flawlessly, and I just wanted to kill her. There was one thing that sort of wrecked the acting side of things for me and that was when the people in line behind me pointed out that Emma Watson basically only acts with her eyebrows. I watched the movie, noting the scenes she was in, and well, that person was right.
In the end, though, I think I can only part with a 4/5 at best. I was disappointed about how fast the movie progressed. Sure, there's got to be give or take somewhere. The thing that sort of makes me upset, though, is that the longest book gets condensed into the shortest movie, and I don't think it was for the better at all. Quidditch gets completely cut, which, overall is okay. In the book, it was just another layer to the Harry-Ron thing, not to mention the fact that it also inspired more hatred for Umbridge. Granted, this is a minor gripe, but these kids are at school...do they like...go to class? Sure, they showed all of Umbridge's HI scenes, but still.
The thing that actually rubbed me enough of the wrong way to knock the film down a star/rating is the way that the Ministry Climax and Fred/George leaving was handled. I mean, the Ministry scene at the end is arguably one of the most exciting scenes in a Harry Potter book to date, whereas Fred/George capture the spirit of the twins impeccably. Since the movie was only 138 minutes (first=152, second=161, third=141, and fourth=157, so don't tell me the longer movies couldn't be successful) it would have been nice for them to throw another 20 minutes or so on to at least do the Ministry scene justice with the Department of Mysteries. As for the scene itself, I was disappointed with the somewhat random (IMO) portrayal as Death Eaters flying all about. It didn't match up to the scale in the battle scene for me. Finally, I think the Dumbledore/Voldemort showdown was pretty lame. I'm glad that I didn't pay to see it in 3-D just to watch THAT. Fred and George's exit was just woefully short as well, IMO, because they do SO much in the book.
I didn't know whether or not to throw a spoiler tag up, so I will do one for safety.