I was greatly peeved at how many times Jackson expanded a 1- or 2-sentence mention in the book into major scenes. See Radagast and the stone giants for prime examples.
I think a PJ-style movie adaptation of The Hobbit would have fared well as a 3-hour theatrical cut, plus some extras for the Super Deluxe Director's Extended Blu-Ray Edition.
And why the hell didn't Bilbo's actual finding of the Ring from The Hobbit match the scene from the first LoTR film? Can't Jackson follow his own freakin' canon?