In many ways, this is the same Potter, all grown up. A prevailing theme is that everyone at Hogwarts is trying to find love. This search is bolstered through the discovery of a love potion which they learn how to make in Professor Slughorn's potions class (oh, yeah, his return to Hogwarts booted Snape into the Protection Against the Dark Arts class, the standard bad-guy position.) This subplot made for some interesting, hilarious and heart-felt episodes with various members of the cast.
In fact, there are several subplots in this movie that all somehow revolve around the main plot: who's trying to kill Dumbledore and will they succeed? The who is answered rather quickly, the success is interestingly measured. But I say that's the main plot only because it seems to be the only plot that comes to a satisfactory end. In many ways, even this plot circles around an even greater plot: "What is Voldemort planning, and how can we stop him?" The problem is that this plot never comes to an end.
At the end of The Half-Blood Prince, one is left sitting in the theater wondering if that's it. The ending feels more like a commercial break than any kind of conclusion. As if the movie realizes we've been sitting in the theater for almost three hours wondering about the fate of Dumbledore and it's willing to give us an hour or two break before we come back and finish the movie. The thing is... there is no more movie. I understand the concept of it being one in a series and that it should be leaving us begging for the next one, but plenty of series movies (I can think of at least the Lord of the Rings trilogy) wrapped up their plots quite nicely in the middle of the series leaving you satisfied until the next movie came out. It can be done, and I think it ought to be. When we come to the end of the movie we finally find out what Voldemort's weakness is. It's like the climax of the story! We know how to defeat him! Hurray! End. >.> Uhh... So, we're just gonna... not defeat him, then.
Again, I understand this part of the story will be fleshed out in the next couple of movies, but you could at least give me SOME kind of closure. Even the plot against Dumbledore seems hollow and unexamined. Well executed, to be sure, but in the end... now what?
Ok, there it is; my scathing criticism of Harry Potter and the Half-Blood Prince. Really, though, I thoroughly enjoyed the movie. Granted, I was following the wrong plot most of the time, but I enjoyed the ride. This has all the ingredients for a great movie, a lot of eye candy, a lot of brain candy and a lot of heart candy. If you're looking forward to this movie I dare say you will not be disappointed. Especially if you know what happens in the last book.