If thou hadst world enough and time / This shyness, Harry, were no crime
Do not read on unless you've read Harry Potter and the Half-Blood Prince. Not only will you spoil and excellent book for yourself, due to the magical nature of this post your eyes will rot and fall out of your head. You Have Been Warned.
I've thought a lot about Harry Potter and the Half-Blood Prince lately—in fact, I've really dwelt on it rather unhealthily for the past week. I'm just like that. I've had a lot of thoughts about what exactly happened at the climax of the book, and Snape's true current status, but you can find much better discussion elsewhere. I do, however, want to comment on two specific issues.
First, I found the amount of attention this book focuses on Harry's qualities as a leader, as opposed to a simple actor, interesting. For instance, in the early books the main purpose of Quidditch seemed to be showing Harry as an incredibly talented individual: the characters go on at great length about Harry's completely unmatched skill, and throughout the series Harry's team actually never loses a match that Harry plays in without interference (and isn't attacked by dementors, and doesn't have his own Keeper knock him out with a bludger).
Harry's skill is reemphasized near the beginning of Half-Blood Prince: Harry and Hermione play two-on-two Quidditch against Ron and Ginny, and since Ron and Ginny are both quite good and Hermione is dreadful, they wind up about evenly matched. Because of this, it's hard to make the Quidditch games interesting; Harry's just too good for his team to lose without something strange happening. So in Half-Blood Prince the focus is on Harry not as a player, but as a captain. The most important part of the first game is Harry's ability to manage his people and find a way to get Ron playing in top form. And Harry doesn't even play in the most important Quidditch game; but he's the one who shaped a team that could slaughter Ravenclaw three to one, and he gets credit for the victory.
I think this focus on leadership is a preparation for Harry's taking a more proactive role in book seven. For most of the books Harry is fundamentally reactive: he goes to school, and then stuff happens to him and he does what he needs to solve the problems that get thrown at him. In book six he becomes more active, going out and trying to solve the mystery of the Horcruxes and helping Dumbledore retrieve one. In the DA, he has a group of people loyal enough to him to do what he asks them to; and he's willing to act independently and use them to take risks and stop threats he perceives. At the end of Half-Blood Prince we find that in book seven Harry will be totally proactive, finding Voldemort's four Horcruxes and finally defeating Voldemort himself. He's completed the transition from the whiny, angsty teenager of Order of the Phoenix into a mature young man capable of bringing down the most powerful wizard alive.
But one part of the ending really bothered me. After the funeral, Harry tells Ginny that they can't see each other anymore, because it wouldn't be safe for Ginny—Voldemort might attack her to go after Harry. This idea really annoys me whenever it comes up (the recent Spiderman movies, for instance), and it seems even sillier in this specific case. First, it's not like Harry and Ginny have exactly been hiding the fact that they're together before this; Snape certainly knows, and Harry thinks Snape's completely loyal to Voldemort. If Voldemort really cares, I think he'd be able to find out, whether or not Harry and Ginny are still openly dating.
Second, it seems almost patronizing to Ginny. If Harry respects and cares for her, I'd think he'd let her make her own decisions; she knows the risk, and if she's willing to accept it, it seems intensely arrogant and paternalistic to try to protect her by keeping her away. I understand that Harry doesn't want to see her hurt, but it's impossible to protect people from everything that might get them hurt. It seems like it should be Ginny's choice at least as much as Harry's.
Third, and sort of as a derivative of the first two, it just seems like such a waste of time. Both Harry and Ginny are in mortal danger; I'd think they'd want to take advantage of all the time they had available. That way, if Harry/Ginny dies, Ginny/Harry can look back and say, "Well, at least we enjoyed the time we had together, rather than waste it worrying about everything that could wrong." As it is, Harry's making both of them unhappy in the short term for dubious long-term benefit, and wasting time that's scarce enough already. I really just want to quote Andrew Marvell at him to try to bring him to his senses.