Wow this was a real page turner, the only reason I put it down was because I was splitting time with my wife. I really enjoyed the fast paced action of the book but there were a few things I found lacking and in some cases disturbing
Spoilers - Highlight to see.
The deaths of Lupin and Tonks get a one line mention? What is that? Lupin was if not a major character he was a significant secondary character. I even missed it, my first clue was when Harry used the stone in the forbidden forest and Lupin appeared.
Did Mrs. Weasley use avada kadavra Bellatrix? Some people have already suggested as much. I don't think she did, even as mad as she was she would not resort to a spell she despised so strongly. I think it is more likely her spell was cast sufficiently strong that when it hit on the heart it stopped the heart. A legitimate idea since a sufficiently powerful physical blow can stop a heart.
This I found most disappointing, Harry's blase use of unforgivables. Rowling acted like these spells were unforgivable for a reason. That and it was completely unnecessary when he used crucio just because the guy spit on his prof.