Hits and misses by category:
Hit: This is the toughest category to pick just one favorite, since I read so much outstanding children's fiction this year, including the Roman Mysteries series, the Kane Chronicles trilogy, the second book of the WondLa trilogy, the New Olympians series, and the Incorrigible Children of Ashton Place series. But if you held a gun to my head and forced me to pick just one "best" book, it would have to be The Golden Compass, a truly remarkable book that deserves to be considered a modern classic of children's literature.
Miss: I already blogged about my disappointment with Alanna, so I'm going with The Edge Chronicles: Beyond the Deepwoods. The worldbuilding was cool, but you're never given a reason to care about the protagonist beyond the fact that he's the protagonist and you're supposed to care about him. There was no plot, no story goal-- just this whiney little shit stumbling from one disaster to the next. And there was not one but TWO unrelated grotesquely obese female villains, which rubbed me the wrong way, AND one scene had perhaps the most offensive extended metaphor for menstruation (and female maturation in general) that I've ever heard. I was literally yelling at the CD player: "My GOD! Ten-year-old boys are going to read this stuff, you know!"