First, to address the act in the book that is least excusable, most inspired by desire for personal gain at the expense of the feelings and rights of others, but if my younger sister had been in my room, reading my personal letters, I’d have thought death-by-Voldemort too good for her.
I rather enjoyed it, though less I think than I enjoyed Half-Blood Prince. I would have liked less charging around the countryside (though I did like the depiction of the Quest as tedious, time-consuming, and not all that effective as a strategy), and a lot more conversation and confrontation with the Bad People earlier in the book. Flying Voldemort was effectively creepy, and I was entertained in a Schadenfreude sort of way by the use the Death Eaters made of the “I’m so brave, I say his name” attitude of the heroes. I never expected a full explanation of the Werewolf Incident, so I wasn’t disappointed not to get one. I did expected Snape to be Good, though I wish he had lived, and a last year spent as Hogwarts Headmaster was probably not his life’s ambition. The business with the wands irritated me much of the way through, and though I liked Harry working out that he could defeat Voldemort with Draco’s, I didn’t find that worth the rest of it. On the Black front, Molly fighting Bellatrix was both unexpected and effective, and if Voldemort doesn't want her mooning over him, he should have thought about that earlier, Narcissa betraying Voldemort for Draco’s sake lets me say “I was right”, and Andromeda was not a cuddly werewolf-loving mother-in-law (I now need to write a fic in which she is massively annoyed that she is expected to give up everything to look after her orphaned grandchild). Neville’s Gran dashing off to join the fight requires fic. I see from a_t_rain that I am not the only one to assume that Hermione did not ask her parents’ permission before brainwashing them, and whilst I’m sure she’ll be keen on action against the Muggleborn Registration Committee, I’m not convinced that the WW’s attitude to Muggles will become any more enlightened in the near future. I anticipate much Grindelwald/Dumbledore slash (and I was glad to see that Grindelwald had been imprisoned rather than killed). As I first entered fandom the year before Goblet of Fire courtesy of loads of internet-surfing time towards the end of a summer job, google, and the Yahoo! “Harry Potter for Grown-Ups” list (which I never read much, but enjoyed the theories), I was massively entertained that Tew Eww turned out to be true, and it’s a rare children’s book that features goat fiddling.
(ETA: Much as I sniggered childishly at all the wand jokes, I felt this could have been better phrased:
"Hagrid was struggling, and Bellatrix was panting, and Harry thought inexplicably of Ginny, and her blazing look, and feel of her lips on his --")
I loathed the Epilogue, more I think for the shift in style than for the actual content. I’d much rather have had a brief paragraph on each of the major characters than Happy Families, though I was amused by Malfoy’s receding hairline, which struck me as authorial smirk on a line with the revelation that Philip Boyes was bad in bed, without the narrative justification, and am resigned at seeing Harry and Ginny carrying on the old Evans and Weasley family traditions of failing to act against sibling victimisation, thus setting up the next cycle of disaster.
And well done, Dudley.
Lastly, it has all left enormous possibilities for fic.
I’ll start with a very small one.
He had split his soul once, long ago, and later Dumbledore had trusted him because the old man had seen that Snape’s remorse was genuine, had seen the torn soul heal. Now he was asked to split it again, and he knew that however Dumbledore dressed it up as mercy for an old friend, that could not be why Snape would kill him, that he did hate the man, and that for Lily’s sake his soul would, again, be lost.