To be truthfully, personally I liked McKenzie's acting. Yes, it was stilted and monotone...but I honestly think that's what both the dialogue and the atmosphere of YO called for.
And oddly enough, Ive asked 4 or 5 people in the real world what they thought of it, they all said they liked it. In fact, I seemed to be the biggest dissenter among them.
I'm sorry, but I have to disagree.
The color pallet was next to identical to the comics. Outside of the voice acting, I truly believe the big "flaw" that no one can quite put their finger on is the simple fact that Year One is better as a comic book than as a movie. They're two totally different mediums...that don't always carry over.