Okay, as I am one of those crazy people who did actually wait for and then enjoy Harry Potter and the Half-Blood Prince, I am going to devote 3 days to it in my blog. I've read it twice now and (overall) found it measured up to the others in the series. Leaving the reviews to the reviewers, I'm going to focus on The Good, The Bad, and Questions.
1) The writing. The writing and editing in The Half-Blood Prince is much better than in The Order of the Phoenix and parts of The Goblet of Fire despite a few typos here and there.
2) The first chapter races along and drops you directly into the action of the story. I also liked the interaction between the Prime Ministers (although I noticed some of the younger kids interviewed for the Sunday London Times did not like this addition!) Then, in Chapter Two we are whisked away with Dumbledore, while at the same time filled in as to what's been happening in the magical world through newspapers lining Hedwig's cage and Harry's conversations with his teacher.
3) The garden gnomes are back. Need I say more!
4) Ron's appropriately pathetic romance with Lavender Brown is so typical of first relationships, I could hardly believe it. I also like how Rowling acknowledges Ron and Harry are a bit slow in the relationship department.
5) Slughorn! What a great character. Who hasn't known teachers (and others) like Slughorn? Playing favorites, collecting stars, but yet essentially a good person and an excellent teacher.
6) Harry. For the first time I actually liked Harry as a character. She has created a hero who has come through childhood trauma and early adolescence and is maturing into an honorable, good, brave person. We begin to see that he may live up to his promise and curse.
7) Dumbledore's big mistake. This troubled me the first time through. How could Dumbledore, the wise, kind headmaster make such a huge mistake--the mistake that kills him in the end? Dumbledore (or Rowling, who has said--and now I can't remember where--that when she speaks she speaks through Dumbledore or Hermione) explains on p.187 of the British edition: "Naturally I do, but as I have already proven to you, I make mistakes like the next man. In fact, being--forgive me--rather cleverer than most men, my mistakes tend to be correspondingly huger."