The plot, for instance, is very badly paced; tragic and terrible things happen, or at least we're told they do, but we jump from one tragic happening to the other without being given much time to think about them, and worse, without the characters themselves seeming to care much about them.

For example, look at the list of people who die. This is the book, in all of the Harry Potter series, with the highest death count: characters die that have in some cases been with us for the whole series, and that have been with Harry (the point of view from which the story is told) for several years. Still, it feels like the deaths are thrown in for shock value and little else: somebody dies, Harry mopes about it for a few pages and then just moves on and doesn't think about them for pretty much the rest of the book. So do the other characters.

The reader isn't given much chance to care about them, either: with only a few exceptions, the characters dying have either been background characters since their introduction, or have been pushed in the background so strongly that we don't really see much of them. Around the middle of the book, I found myself seriously wondering if J.K. Rowling was trying for a "rocks fall, everyone dies" type of ending. None of the deaths have an impact. I mean...

Charity Burbage (deliberate Avada Kedavra)

I'm guessing the killing of the Muggle Studies teacher from Hogwarts is intended to show the "dark times for Muggles incoming" idea. The problem with it is, it kinda falls flat, because we'd never heard about Charity Burbage before, not even in passing.
Also: before she gets killed, she begs Severus Snape to help her. What are we supposed to think of that - that Snape is cold and unfeeling and oh-so-evil? It smells of a glowing neon sign - "look, look, he doesn't help her, he's evil!" - but what exactly was he supposed to do to help her? Jump on the table in front of Voldemort and the Death Eater convention and declare himself her brave rescuer, and get himself killed as well as her?

Hedwig (stray Avada Kedavra)

Harry is woeful about her for about two sentences when she dies, then again when she's mentioned a couple pages later (twice, first by Hagrid and then by Mrs Weasley), and then the poor thing gets entirely forgotten... which doesn't really make much sense. Hedwig "had been his companion, his one great link with the magical world whenever he had been forced to return to the Dursleys" - in other words, a symbol - so why exactly is she so easily cast aside?

Mad-Eye Moody (deliberate Avada Kedavra)

He dies exactly the way he's been living most of the books since he was freed from that trunk he was locked in - off-screen doing his job. Woe is him, I guess?

Scrimgeour (tortured and murdered)

"The Ministry has fallen. Scrimgeour is dead. They are coming." Another character who dies off-screen, and in his case I'm not even sure what we're supposed to be feeling for him.

Ted Tonks, Dirk Cresswell, Gornuk

Two random wizards and a random goblin. Ted Tonks is only notable because he's Nymphadora Tonks's father; Dirk Cresswell I had to look up (he was mentioned incidentally in Book 6); Gornuk is just a random goblin. Harry, Hermione and Ron run into them by chance on page 242; they are not mentioned again until page 356, when we hear they're dead.

Wormtail (strangulation)

He gets strangled by his own hand for having a moment's hesitation in killing Harry. (Which isn't
really explained, anyway: the hesitation is portrayed as taking even Wormtail himself by surprise.) It's not even a full page's worth of a scene, and feels rather unsatisfying. (And how'd his hand suddenly decide to strangle him, anyway? If it's a part of Voldemort, controlled by him, how come it spared Harry? If it's not, how come it didn't spare Wormtail?)

Dobby (stabbing)

Dobby gets stabbed by Bellatrix's knife moments before teleporting to safety with Harry. I feel sorry for him, and his death was probably one of the most moving. (But still, Harry mopes about him for a few days, then he gets conveniently forgotten.)
My quibble with this death is pretty simple. "Dobby has no master! Dobby is a free elf, and Dobby has come to save Harry Potter and his friends!": that's great, and I very much feel sympathy for him, but - that's quite the character development for somebody who has last been more than an incidental character in Book 2. We haven't seen him much for years, we don't know that much about him, he gets brought back into the spotlight only for the purpose being summarily killed off while getting Harry and friends out of trouble.

Then a bunch of wizards and goblins get killed by a furious Voldemort after Harry, Ron and Hermione successfully steal Hufflepuff's Cup from Gringotts...

Then there's the Big Hogwarts Fight. I have to admit I started reading it fully expecting the end result to be something like "The building gave a great shudder and collapsed, burying everybody who was still inside with the weight of its stones". I'm only half joking, here. D:

Vincent Crabbe (burning to death)

Killed himself, via idiocy. Seriously...

Fred Weasley (explosion)

A rather random death, purely for shock value. Seems to have just been placed there for the sake of "hay let's kill a Weasley".

Severus Snape (bitten by Nagini)

His death has absolutely no impact, because at the point he dies, we, the readers, are still supposed to be thinking of him as evil, because he almost doesn't get mentioned in the book, except for the requisite "hay look he's by Voldemort's side he's EVIL" pointed finger whenever Harry has another vision. (Unless the clues as to the fact that he was still working to aid Harry, as well as the reason for it, were deliberately, rather than accidentally, made so huge and obvious. I don't think so.) It's only afterwards that we find out his past.

Nevermind that it was obvious that Snape was still helping Harry.

A Patronus, in the form of a doe, leads Harry to Griffindor's Sword. We hadn't seen anybody with a doe Patronus before, so it had to either belong to one of the characters who hadn't so far been seen casting the spell, or to a new character. The latter is unlikely (too much of a deus ex machina, even for J.K. Rowling); of the former, the one who is most likely to have access to the sword and have both a motive and a way to give it to Harry is Snape.

Even the "unrequited love for Lily" plot point was rather obvious. Snape's motive is, at the surface, that he's still working for Dumbledore; the doe Patronus, though, points at something else - the connection from Harry's and James's stag Patronus to Lily was rather easy to make. The final confirmation, at least for me, was Snape's last words: "Look... at... me..." - why did he want Harry to look at him? Harry had Lily's eyes, it's a point that's been hammered into us several times in the book.

I thought "The Prince's Tale" was one of the best chapters in the book; I can only wish it had been better placed. If Harry had found out about Snape's backstory before he got killed, at least in part, Snape's death scene would've turned out to be much more dramatic and poignant. As it stands, somebody who's not figured it out already is more likely to be left going "gwuh?" than be saddened.

Nevermind that once he does find out Snape's backstory, he gives it absolutely no thought beyond "right, off I go to get killed by Voldemort". Not even a stray thought about Snape, his feelings, or anything else. The backstory almost feels inserted in that positioning merely in a clumsy attempt to make the reader feel sorry, or even guilty. "Look, here's a man, and he died, and you thought he was evil but he wasn't!"

Remus and Tonks (killed in battle)

Another off-screen death, and even worse in terms of "let's increase the death count" than, say, Fred Weasley. Harry finds out that they're dead upon seeing their bodies in the Great Hall, among the rest of the victims; it's very sad, I guess, for their just-born child, but again, it feels like they're just there for shock value. They're not even in the book very much, except for when it comes to talking about their son (and Lupin's depression about it); they're often presented in small cameos, with very little thought behind them. (In one scene, Harry shouts at Remus because Remus wants to abandon Tonks and their unborn child; the next time Remus pops up, he's all gleeful about his child being born, asks Harry to be his godfather, and runs off again. The argument between Harry and Remus never has a proper resolution.)

Bellatrix Lestrange (killed in battle)
Gets killed by Molly Weasley. Fair enough, and actually a decent duel, though if Bellatrix was Voldemort's "best lieutenant", how come she was so easy to kill? Three students - admittedly, three good students (Hermione, Ginny and Luna), but still students - could hold their own against her, and Molly Weasley of all people could kill her? This was Voldemort's best lieutenant?

Voldemort (killed by his own spell)
Even Voldemort's death is anticlimatic. He gets basically Expelliarmus'd to death by Harry - after being fooled by Harry pretending to be dead (because he sent Narcissa Malfoy to check, of all people, instead of, say, borrowing a sword and stabbing Harry repeatedly with it) and after he carelessly removed Nagini, the last Horcrux, from her protective cage, leading to her getting beheaded by Neville. Sigh. One of the most powerful wizards of all time, and he's this stupid?

In general, the Big List of Deaths just feels - well, the cheap way out, to be honest. Yes, this is war, and people get killed in it; but why exactly is it that only secondary characters die? The closest it gets to the death of a main character is Snape (not counting Voldemort, he's the villain - it pretty much had to end with his death). Harry, Hermione and Ron risk their skin all the time and absolutely nothing happens to them, while most of the secondary characters their paths cross with get killed off.

And speaking of which, how come the trio always, always narrowly escapes from dangerous situations, just in time, by a streak of luck? The Dursleys', the Ministry, Godric's Hollow, Lovegood's house, the Malfoy Manor, Gringotts, and so on.

Everything in the story - not just the escapes - appears to move by author intervention, rather than by the actions of the characters. Horcruxes, and the tools to destroy them, are found by chance (let's not even get into the pure idiocy of Ron simply being able to randomly hiss at the door of the Chamber of Secrets until it opened); when it's necessary for the heroes to get caught and taken to Malfoy Manor, Harry conveniently forgets about the Taboo on Voldemort's name and gets them tracked down; when Harry needs to find Ravenclaw's Diadem, he finds it very easily in a room full of junk (where it shouldn't have been hidden in the first place... prideful Tom Riddle may have been, but such an idiot as to not notice that the Room of Requirement was already full of items hidden by other people?); and so on.

And what's with the Deathly Hallows, anyway? They just seem to be inserted to pad the plot and add mystery; they are never all in the possession of one person at once, so we never even find out what it means to be the Master of Death. The Cloak, Harry always had; the Resurrection Stone is found by Harry inside the Snitch (hi, psychic Dumbledore) and serves as motivation when he goes to get himself killed by Voldemort; the Elder Wand is just a convenient plot point to get Harry to survive an Avada Kedavra again, and be able to kill Voldemort afterwards.

Another thing that annoyed me: the Dumbledore subplot.

We get the "Albus Dumbledore was a saintly man" version of the summary in the Daily Prophet on pages 21-24, Rita Skeeter's vague insinuations right after that (pp. 26-29), more insinuations from Auntie Muriel on pp. 128-132, Rita Skeeter again on pp. 178-180... then the Big Revelation on pp. 288-295... and then nothing much, except for a passing mention on page 320, until the meeting with Aberforth on pp. 451-458, in which the truth is finally revealed.

My problem with this is very simple: this is about a man who Harry almost idolizes. While Harry is running around with Ron and Hermione, looking for Horcruxes to destroy because Dumbledore told them to and they trust him, Dumbledore's Golden Aura of Goodness is being chipped away, in bits and pieces, by people and facts that appear to fit together and make a lot of sense. Does Harry think about this? Does he hell. Except when he's looking at a piece of evidence, he almost never remembers to ponder the implications. He finds some more information, has a brief Dumbledore-related angst moment, and then moves on and forgets about the whole thing until the next piece of info turns up.

When the truth is finally revealed, Dumbledore is restored to his golden pedestal, and Harry manages to completely ignore exactly how utterly nasty and cruel Dumbledore was to Snape in Snape's memories, and even forgives him for lying and hiding things (getting almost to the point of blaming himself for not seeing the truth, rather than Dumbledore for hiding it).

And lastly, let me get something off my chest (emphasis mine):

"'Dobby, is this Shell Cottage?' he whispered, clutching the two wands he had brought from the Malfoys', ready to fight if he needed too."

Proofreading, what proofreading? I can't believe that got through. D:

Um. I think that's all. I'll probably end up editing this as I remember more things that annoyed me. :P

[EDIT] Oh yes - retarded moments:

"Accio Hagrid!" - By the time Harry shouts this, it's been at least a few minutes since Hagrid jumped off the motorbike. If we listen to the law of gravity, he's probably hit the ground already. Nevermind the idiocy of using the Accio spell on a person; when Harry tries casting this spell, he's still astride the flying motorbike, which is plummeting towards the ground at great speed. What the hell is he trying to do - fetch Hagrid back up so he can slam him into the ground again, just in case the fall didn't kill him the first time? D:

The Great Metaphysical Train Station - and here I was hoping I would no longer get to read Dumbledore spouting pseudo-wisdom at Harry. That was just cheap.

The epilogue - 19 years have passed, and Harry and company still act like teenagers. Meh.

[EDIT #2] *dies laughing* And already icons are popping up with "AS/S" (Albus Severus / Scorpius), including "'All was well' my AS/S", "Time for some AS/S", "JKR finds her epilogue embarAS/Sing", and suchlike. Oh, fandom.