The book was alright, but there were a lot of plotholes or just instances of bad writing such as when they introduce the "laws of magic" such as you can't make food, only increase it's amount. Why then can't they just get a little food and then increase the amount of that by a lot instead of whining about hunger?
You're a wizard, Jesus!
The magical rules have always been full of holes (couldn't a poor wizard just duplicate coins or something?) so I try not to dwell on them too much. I did get a sense in this book though that she had to try and paint her way back out of some corners. Why was the invisibility cloak so special all of a sudden in this book? She had done an all right job of hinting at future books in earlier books, but the deathly hallows kind of came out of nowhere, and some of the magic stuff did seem a little strange.
I thought the ending was a little too "and they lived happily ever after THE END SO THERE" ... and none of them seemed to end up being important? It was like the point of the epilogue was to just prove that those couples got married and gave all their kids stupid names. It seemed to sort of trivialize the series- is that what they were supposed to have gotten from the whole series? I'm sure I'm not the only one who's going to pretend that epilogue didn't happen. :) If she were going to talk about what was going on 15 years down the line, I'd have a whole other list of people I'd much rather hear about. I already knew those guys would have happily ever afters.
I did like most of the book, as other said, there weren't many surprises but it was satisfying. The first half of the book really dragged. I'm sure that was meant to highlight their total lack of planning, but it made the end of the book go way too fast and seem a bit too 'easy' if you know what I mean. There was some interesting stuff though - more about goblins, the stuff with Fred and George was good (would have liked more), lots of fun bits with Molly, Dobby not being annoying for once, and even Hermione making some dumb mistakes.
I also didn't mind that certain people died, but that they were killed so offhandedly was kind of a disappointment. I know she can't give everyone a detailed death but some of these characters are pretty beloved- and the point was that Harry was deeply affected by these people who were so important to him- but they get all of two sentences telling the reader they're dead. That's not going to create much of an impact with the reader, so less chance they'll empathise with Harry.
I thought though at one point Rowling had said "Harry's not the 6th Horcrux and he won't die at the end of the book" ... I was annoyed that she copped out of that by making him the 7th Horcrux and him sort-of-maybe dying. T_T