I have emerged from the other side. Got the book at 9 in the morning of the 16th, read two chapters and rushed off to work. After which I devoted the entire evening, night and the following morning reading the book.
I like the Harry in this one much better then the capitalized Harry in OotP. Lots of romances going on. Hormones and jealousy flying high. Some bits of teenage drama going on there, but I guess it should be expected.
Lots of information revealed, especially on Tom Riddle/Voldemort. But there are some spots I wished JKR elaborated more, like Harry's grief for Sirius. How he worked out he shouldn't continue acting like a prat, etc.
I wish there was a lot more Lupin too (cuz he's my favourite), though we did get to hear what he was up to and even a little but of his history. And of course he and Tonks hooking up was the best thing ever. XD I went through a phase of intense Remus/Tonks shipping right after OotP. It isn't one of those ships that we know for sure that might sail in canon. Hermione and Ron are obvious enough. Bill and Fleur were mentioned slightly in book 5. Even Ginny and Harry seemed like an eventuality though she insisted that she "gave up" on him.
The indentity of Half-Blood Prince... I was kind of proud of myself on this one. When Harry mentioned miniscule writings I immediately thought of that pensieve scene from book 5 where Harry described Severus Snape's handwriting as tiny. Of course, the Half-Blood Prince being a potion's expert and inventing Defensive spells are major tip-offs. The publish date of the book threw me off slightly but it's not entirely impossible for Snape to get a second hand book. The irony of course is Harry appreciating young Severus's notes while hating Snape's gut.
Dumbledore's death wasn't as much as a shock as the manner of his death. We all suspected that Dumbledore will die some point in the series. And his withered hand didn't bode a very good omen throughout the book. But Snape betrayal... well, we did receive some hint in chapter 2, but he very well could be bluffing in front of the Black sisters. The Unbreakable Vow didn't look too good to me though, and it was frustrating how Dumbledore trusts him so much. It was frustrating too that for once Harry was right to suspect Draco and Snape but nobody really believes him.
I cried when Dumbledore died. Well, not really. I cursed Snape when he killed him. I cried afterwards, don't remember when, it was either before, or after the Hospital Wing scene. His death was such a tragedy. What with the betrayal and the pointless drinking of poison.
Closing the school came as a little surprise though it shouldn't. What with Dumbledore murdered on Hogwarts ground. And as for Harry, Ron and Hermione leaving school and search the Horcruxes on their own... I guess we shall see how it is done.