I've finished the book, but my thoughts will take a little while to sort themselves into proper criticism; for now, if you don't mind spoilers, start with Russell Arben Fox and Eve Tushnet and work your way deeper into the internets from there.

Update: It doesn't deal with Deathly Hallows, but I quite liked Megan McArdle's piece on the economics of Harry Potter, or "Why are the Weasleys poor?"