Fantastic.

Rating: 10/10 (4 September 2007)

Top marks; an excellent film. I'm not sure if I prefer this or Prisoner of Azkaban, but the films are neck-and-neck.
One of the things I find about watching any of these films is that, as a die-hard fan of the texts, I find it difficult to escape critiquing the film as adaptation as a watch it; I know how the scenes play out in the books, who gets the cool lines, and how plots intersect, and so I observe how the filmmakers rework it on film; this was true to an extent in this film (moments like when Sirius, rather than Moody, gives Harry the photo of the old Order; or Kingsley getting Phineas' "style" line), but, as I was on my way home, I realized that I had completely overlooked the way the filmmakers rerouted the villains' scheme in the end, jettisoning Kreacher's involvement entirely. So, they can pull me out of the canon on occasion, and that's pretty impressive.
Also, the repeat of the "I must not tell lie" line (which I guessed two seconds before he said it) was an excellent addition.
The only things I really miss here were the encounter with Neville's parents at the hospital (the scene between Harry and Neville in the RoR is a decent substitute) and all the Umbridge v. McGonagall stuff (we get a truncated version, but I really wanted the career consultations scene; Maggie Smith would have been awesome in that).
The action the Department of Mysteries was excellent; in particular, the arrival of the Order of the Phoenix as clouds of white smoke was a real "yeah, the cavalry" moment, and the choreography of the initial encounter between Harry's team and the Death Eaters was brilliantly claustrophobic. By comparison, the Dumbledore vs. Voldemort fight was kind of anti-climactic (in an interesting choice, Voldemort seems to really overpower Dumbledore here, while in the book it's more of a clear stalemate).
There were the usual clutch of stellar performances from the entire British theatre guild. It's become perfunctory to say that Alan Rickman absolutely rules all, but he still does. The kids are all terrific here, and there's actually some effort made to set Ron and Hermione up (although Radcliffe and Watson still have more chemistry on film). The girl playing Luna is really, really good. On the villain side, Jason Isaacs delivers another of his "smooth criminal" performances, and Lucius remains the series' best villain; at the same time, Ralph Fiennes' Lord Voldemort is way, way better here than he was in GoF (where I was a bit underwhelmed); Helena Bonham Carter has few lines, but she's effectively creepy/deranged. And Imelda Staunton is great as Umbridge (as I knew she would be as soon as I saw Vera Drake).
Yates' direction is great (very much like Cuaron's), and he and the screenwriter make some inspired stylistic choices (they get a lot of mileage out of the things the Room of Requirement will do to suit the needs of the people inside). I also want to mention the way that Ron and co. escape the Inquisitorial Squad, which I have to say I like much better than the method in the book.