(spoilage factor: about the same as any drink that Malfoy gets his mitts on)
Harry Potter and the Half-Blood Prince is an example of how a movie can contain a lot of good scenes without actually being a very good movie.
The sixth installment in the franchise brings the boy wizard and his gang back to Hogwarts for what's supposed to be another year of schooling, but instead turns into two parts teenage angst and one part magical mayhem. There's a significant amount of tonsil hockey going on as some of our young heroes get to know their classmates better, and those who aren't in on the action are pining away on the sidelines for their unrequited loves. When they're able to pause for a breath, they find that someone's been setting deadly traps for their schoolmates, meanwhile Harry comes into possession of a Potions textbook where someone called the Half-Blood Prince wrote all of the answers, and there's an occasional attack by the badguys. And then there's some stuff about Tom Riddle/Voldemort once in a while that really isn't about He-Whose-Name-Must-Not-Be-Spoken so much as it is about Harry trying to get a teacher to reveal something about an incident with the future-dark-lord but not really getting anywhere as the teacher refuses to fess up, and those scenes felt kinda creepy, especially the way the teacher stared at Harry. Once in a while Voldemort makes an appearance as a snotty little bugger only barely restraining his viciousness in somebody's reminiscences of him as a school boy.
The problem with this movie is that there's way, way too much going on in the story to cram into a couple of hours of screen time. But the film doesn't realize this and tries to fit in all the bits it can anyway. Unsuccessfully.
This is most obvious in two plotlines that didn't get anywhere near enough screen time to properly explain them to make them worth the bother, or, most importantly, to make us care. The first was the mystery behind the so-called Half-Blood Prince mentioned in the annotated/graffitied Potions book. Harry gets the book, reads the name, basically goes "huh" and gets on with exploiting its bonus notes. Hermione, as usual, gets jealous then righteous and says "you shouldn't use that!", to which Harry more or less replies "meh" and continues. There's one, maybe two more times where they ask in an attempt at earnestness who the HBP could be, but we're never really given any scenes of Harry actually trying to find the answer. More importantly, it's never really conveyed to us why the answer matters. This leaves us in the end, when Snape spills the beans, not really caring. Oh, you just murdered Dumbledore and it's supposed to matter that you've also made some revelation about scrawling all over a book that really hasn't done much except get Harry good grades and give him a spell to shotgun Malfoy? How could we possibly care?! Dumbledore's just taken a nosedive off the top of the tower, and the rest of the movie was pretty much entirely concerned with teen love lives to a degree not seen since the Molly Ringwald films of the 80s, and somehow this book is supposed to matter?! The flick hasn't gone to the effort to show that the story hinges on this book at all! More effort was needed here, especially since the alias in the book is the title of this installment in the series.
The other plotline that was highly problematic was the childhood of Voldemort. There just wasn't enough to matter. Okay, he was a disturbing and disturbed kid. From his adult behaviour in the other films (we won't go into the books because adequate time was taken in them to make this plot line relevant) we pretty much already guessed that. These scenes were brief, nowhere near as powerful as the entire Riddle family history, and Tom's story specifically, as outlined in full in the book, and ultimately, for the purposes of this movie, were entirely pointless. There was no context (like we got in the book by seeing the family story) that gave them any meaning. Think about it, what would the structure of this film have lost if the director had removed the Riddle scenes? Nothing! We would have had a plot that looked something like this: Harry meets up with his friends and they go to school, there is snogging and pining, Malfoy behaves like a douchebag as usual, more gawky teenage love and angst, Harry and Malfoy scrap it out, insert more kissing, holidays arrive and so do the Deatheaters, back to school and back to relationship woes, Quiddich!, more snoggifying encounters, Harry and Dumbledore go looking for a horcrux and say hi to some zombies, back to school for murder most foul and some apparent betrayal, Harry resolves to go questing and kick some ass while it's implied that Ron and Hermione will engage in some practice mouth-to-mouth resusitation. See? Nothing's lost by the absence of young Master Voldemort. It's as though they panicked and said to themselves "Oh shit! We can't have a Potter movie without old snakehead in it! A scene or two of him as a kid will keep the audience happy!" (and let me add that the scenes with Hagrid felt pretty much the same). It would have certainly been a tighter film without him.
And that's fundamentally the problem with this movie: there were a lot of really well-acted, well-written and well-composed scenes (and that includes the mushy puberty love and angst scenes because they made the film very believable in the sense that its main characters were teenagers), some of them very funny or poignant, but they just didn't fit together into a well-made film. It was a great, shambling shitmix of a thing with all kinds of spare parts/scenes dragging along in its wake and sticking out in all directions. The Potter movies thusfar have done a great job of holding to the major plot points in the books they were based on, but HBP was just too big and complex to try to fit everything in. Director David Yates should have had the guts to either make some cuts to keep this thing focussed, or to have split the story into two movies the way they're going to be tackling the finale, Harry Potter and the Deathly Hallows.
I don't regret paying to see Harry Potter and the Half-Blood Prince on Saturday, but because I didn't really see a cohesive movie, I do wish that maybe I'd waited to see it on video.