Okay... sorry for the long post, but I have a lot to say about this. Hopefully you'll get something out of it.
Easily the best film of the series. 1-5 were all good movies, but they all had a few flaws that kept them from achieving true excellence. The first two films suffered from the inclusion of too much
info from the books. On the other hand, Prisoner of Azkaban didn't have quite enough
exposition. Goblet of Fire got a couple things entirely wrong, especially Dumbledore's character. He would never, ever grab Harry and yell at him. To me, that slightly diminishes the gentle old man quality he is supposed to have. Order of the Phoenix, as good as it was, failed to completely nail home the relationship between Harry and Voldemort. Half-Blood Prince is the first film in the series that doesn't do anything wrong.
The first five films suffered suffered because the filmmakers didn't entirely know where the series was going. Conversely, Half-Blood Prince benefits from the knowledge of how the series will end. If you're observant, it's full of details, nuances, and hints of things that will happen in the final two films.
I can't stand people who think the movie should be exactly like the book. A lot of the stuff in the book would be confusing and/or look foolishly out of place in the movie. For example, the opening scene of the book (in which the Minister of Magic informs the Muggle Prime Minister that recent tragic events are the work of Voldemort) would be too talky and very confusing. In the movie, we get to see
Death Eaters take down a bridge and ravage the wizarding community. It's much more dramatic, and it effectively establishes that everyone
is in real danger. The same goes for the attack on the Weasley house. No, it wasn't in the books, but it's a better way of showing the true danger they are in (rather than just reading the names of people who have died in the Daily Prophet, like in the books). The sense of dread, and danger is really done well. My point is, that almost all the departures from the book are for the better.
The romantic parts are really funny... really great stuff. Half-Blood Prince is about two main things: The Harry/Dumbledore relationship, and the beginnings of the inevitable romances. I think the film does a brilliant job setting up the Ron/Hermione relationship... I really appreciated that a lot of these scenes were taken verbatim from the book and/or improved upon. The Harry/Ginny relationship felt a little underdone, but it's adequate enough.
While some Potter fans will probably disagree with me here, I think the Harry/Dumbledore parts are exceptional. No, of course they can't include all of the memory sequences from the book. But we get to see the two most important ones. In the first, we get to see Dumbledore recruiting young Tom Riddle from the orphanage. We can see he already has a knack for collecting objects that aren't necessarily his. Then in Slughorn's memory, we see that he is interested in splitting his soul, and storing the pieces in various objects. This memory sort of confirms
what Dumbledore has been suspecting: that Voldemort has taken great steps to immortality, splitting his soul into seven pieces and storing them in different objects. I was worried that we wouldn't learn enough about the Horcruxes that have already been destroyed, but indeed, Dumbledore reveals he has already destroyed a ring, and that Harry has already destroyed Tom Riddle's diary from the second film. Appropriately, that leaves four horcruxes, plus Voldemort himself. In the book, Dumbledore's extensive studies of different memories leaves him (and Harry) with a good idea of what the remaining horcruxes are, but in this film, Harry has no idea what they are. However, I'm sure the next film will fully explain everything horcrux related. I also like the little detail of Harry twitching his head like Voldemort does (after touching the ring)... it's a very subtle hint about a very crucial
plot element in the final chapters of book 7, movie 8.
The final half-hour is pure cinematic greatness. Dumbledore has his finest on-screen moments... moments that propel him past Gandalf, Obi-wan, and any other old, wise, mentor. When he produced the ring of fire, I got tears in my eyes for the first time in the entire series. Then of course, the events after that scene are wonderfully depicted... more powerful than in the book, in fact. Harry has a choice, and he trusts Dumbledore who trusts Snape. The scene with Snape and Dumbledore arguing is one of the strongest scenes of the series. It works exactly how it should: It looks as if Snape is sick of putting himself at risk being a double agent for Dumbledore. However, as some of us know, the heart of the matter is something else. You can tell that that scene was filmed with book 7 in mind. The same thing goes for the actual killing of Dumbledore. It has nuances that were not present in the novel. That being said, the two strongest performances in the film come from Alan Rickman (who has always been the best in the series) and Michael Gambon, who finally gets some decent material to work with. I can't wait to see Rickman's final performances as the strongest character of the series, and I'm also quite excited for Gambon's one last scene. All the other actors are great, like always. However, I was a little disappointed with Tom Felton as Malfoy. Sure, he's very convincing ("I've got to kill you, or he'll kill me"), but I think he could have done much more with the role.
Okay, I don't want to get into too many more details. So to sum up, the movie opens brilliantly, immediately establishing the Dumbledore/Harry relationship. The majority of the film focuses on characters... and it's definitely the strongest character development of the series so far. The film is funny, dark, and most importantly, emotionally powerful in all the right spots. Overall, it's a perfect film. Not exactly like the book... but it doesn't, and shouldn't have to be. Yes, it does feel like just a big set up for Deathly Hallows... but that was always the intention. If there's anything bad about the movie, it's that we're left wanting more. Since I've read the entire series, I almost feel slighted, because I know there are bigger and better things to come... they're clearly purposely saving a load of information for the epic finales. Half-Blood Prince is a truly excellent film, but still not quite the epic cinematic achievement we know the final two films will be. November 2010 and July 2011 can't come soon enough.
The series so far:
Harry Potter and the Sorcerer's Stone: 9/10
Harry Potter and the Chamber of Secrets: 9/10
Harry Potter and the Prisoner of Azkaban: 9/10
Harry Potter and the Goblet of Fire: 8/10
Harry Potter and the Order of the Phoenix: 9/10
Harry Potter and the Half-Blood Prince: 10/10
Alright, that was easily the longest post I've written.
I'm very interested in seeing you guys' reactions, readers and non-readers alike. I'll undoubtedly have more to say later...