I really don't have anything insightful to say about Potter, but that won't stop me from talking about it!
I read the first book, liked it well enough, didn't read anymore. But, as a movie buff, I see all the films. They strike me as fine, if sort of workmanlike, excepting Cuaron's third one, which, as every critic likes to point out, quite obviously benefits from having someone behind the camera to bring something truly "magical" to the imagery. The others are almost interchangeable to me (if you showed me the second one and the fourth one, let's say, I might not be able to tell the difference except that the kids look older!).
Still, as a whole, the series is much better than it could have been. Even if the films were awful, they'd still make a fair amount of money. But they're not at all awful and, in fact, reveal a fair amount of...care. The casting of the three child leads, of course, was a huge gamble, and they've all settled into their characters quite comfortably by this point. It's easy enough to think of them as their characters, as opposed to actors, a problem which I'm sure will plague them forever (did people go see Equus on Broadway to revisit a great play or did they go to see Harry Potter get nekkid?). And the new film strikes me as consistently better than the last couple, perhaps because things are getting inevitably darker. More is at stake (and Dumbledore is dead!). Is this The Empire Strikes Back of the series? At any rate, Half-Blood Prince is a pretty enjoyable summer blockbuster, and we haven't had too many of them this year.