So I've watched the trailer for Harry Potter and the Half-Blood Prince several times the past few days. A few notes:
1) I think it does a terrific job of establishing the mood of the story, which is tremendously dark (if you've read the book, you know it doesn't have a happy ending). But what strikes me about the trailer is that, heading into the sixth movie, whoever edited it assumes that the audience knows who Dumbledore is talking about when he says "the most dangerous dark wizard of all time". Sure, we see a flash of Voldemort, but we're never told that he and Tom Riddle are the same person.
In fact, Tom Riddle is never referred to by his full name at all. He's simply "Tom". Yet the trailer's sense of foreboding doesn't really work at all unless you know who "Tom" is and why he's important. That's remarkable, to me.
2) As much as I would have liked to have seen Richard Harris get to play out Dumbledore's story arc, the trailer makes me realize that he would have looked ridiculous in the flashback stuff in HBP, a very Dumbledore-centric movie. Michael Gambon probably looks older than the character should here, but he doesn't look feeble, which Harris invariably did in his last few years as an actor. Say what you will about Michael Gambon's Dumbledore, but he should capture the young man better than any of the other casting choices who were bandied about after Harris's death (Peter O'Toole or whoever).
3) Has there ever been a movie series that made it to six installments with this much of its cast intact? People seem to like On Her Majesty's Secret Service, but it's still the first Bond movie without Sean Connery. Revenge of the Sith had a few cast members from A New Hope, I suppose, but not this many.
Other than that, how many movie series have even made it to six? Halloween, Nightmare on Elm Street, Friday the 13th. That's about it, isn't it?