Two Face was done well, but they didn't do him perfectly by any means, they left out quite a few aspects of his character I would have liked to see.
For starters, it didn't even look like he had a split personality. It seemed like he was still Harvey, he just wanted revenge. That was disappointing to me. And while they showed his obsession with duality a bit, they didn't show how important it was to him. We never got the sense that he would go nuts if he didn't have his coin. I definitely thought there was much more they could have explored with his character.
And I'd say the look was average. It just went too far, it was very unrealistic. A man with a burn that severe would be dead. Not only that, it seemed a bit cartoony that he could still move his eye, and that his eye was undamaged except for his eyelid being burned away. It was just a little too far, seeing those strands of muscle move when he talked reminded me of the mummy.
I didn't think it was horrible though. I liked it more then Forever, I just thought they went too extreme. I want something in the middle between what we got, and how Mel Gibson's face looked in "The Man Without A Face"