I think it's supposed to be predictable, in a sense. The series has gotten past the point of tricks and turns and reached a point of inevitable finality. We know, from the start of the book, from the start of the very first book, that Harry will have to fight Voldemort and that at least one of them will die. By the time we reach the seventh book, it has picked up so much momentum, we're being driven along by fate and nothing can stop what's going to happen. Maryjane mentioned that a frequent theme of the books are choice, and that's true. But by now the choices have been made, and we must see their consequences. And honestly, some choices are merely illusions, choices that must be made a certain way. Dumbledore tells Harry he could just board the train and move "on", but we know that won't happen. It can't happen, because of who Harry is and what he must do.
My point being, I don't think you're supposed to be surprised by anything, or at least not by much.
So now for a few random comments about the book:
I'll be honest, I hardly read the books for the plot. The plot's nice, but I read it for the characters (as I think most do). The plot certainly helps reveal the characters, their backgrounds and motivations and flaws and triumphs, but that's its primary purpose. So I love the parts where the characters are gathered and content. There's very little of that in this book, but there's some: the wedding, Shell cottage, a few of Ron and Hermione and Harry's moments together. I liked in the previous books where we'd just see the characters talking and going about a normal day at Hogwarts. That was the charm of the books, really. So I liked those moments, few as they were here.
However, I also liked the first half of this book, where at nearly three hundred pages in or however much they still haven't found any Horcruxes, and things seem more desperate than anything: they have no plan, no clues, Ron leaves them, Harry's wand breaks, and every turn they take leads them into more danger. And then, in one moment, when Harry sees the doe, gets the sword, and reunites with Ron, from that point on everything skyrockets toward victory.
I predicted quite a lot of what happened in this book. I knew Snape would be vindicated; the way Rowling wrote the scene of Dumbledore's death, the way the two looked at each other before Snape cast the killing curse, I knew it had been arranged. I was not sure why, though. I think his love of Lily was brilliant and added so much emotional depth to the book. Another recurring theme in the book, and I suppose it relates to Choice, is children and how they grow up. That disparity between who a person is between their youth and adulthood, and the factors that affect it. No one in the books is perfectly good or perfectly evil, even Voldemort (although he has become, perhaps, wholly evil). There is choice involved. But we're forced to consider the factors that lead to what choices are made. We see Harry, sheltered and kept safe for most of his life, and having a pretty miserable childhood. But when he turns eleven, he's instantly introduced to a place he can call home (although the same can be said of Voldemort, Riddle, and others). But he was not raised on thoughts of dark magic and lineage, he is instantly united with people like Ron and Hermione, Dumbledore, Fred and George, people who care for him and instantly put him on the right track. Voldemort didn't have this guidance, and it seems he probably had a more miserable childhood than Harry. Snape was torn between a loyalty to his family, what he'd been raised and conditioned to believe, and his love for Lily. We feel triumphant when Harry succeeds, but we also feel immense pity for these others, those who haven't exactly won, who made the wrong choices, and maybe only because they weren't introduced to the right circumstances. We especially feel for Snape, who managed to make the right choice in spite of immense pain and still died alone, with only a trace of solace, seeing Harry and looking into his eyes for a moment, knowing that he would learn the truth.
Anyway, I've probably said way too much about this. Just a thing or two more.
First off, I also felt weird about the epilogue. I don't think it's bad, per se, and I liked aspects of it, but I feel it jumped too far ahead. I would have liked a moment of peace just a day or a week after the finale, a gathering of friends looking toward the future, still needing to get over the tragedies and to rebuild, but to do so together. A note of ambiguous optimism.
Dobby dying was sad, but not unexpected, and a noble death. The one that really caught me off guard was Fred. I'm still reeling from that one. Like they said in the book, how could things exist without Fred? Maybe it's just me, because they were two of my favorite characters, and both seemed to need each other to exist. That one hit kinda hard.