I heard complaints about the look as well, and all that, but it looked pretty disturbing which is what made it effective for me. They could also show him from the burned side every time he flipped out, that'd be effective.
Pure set up would be nice, but with that ending where they preserve his legacy, death was the only choice.
Just give me 30 more minutes and concentrate the action between Batman and Two Face.
I agree that it's not perfect, but Two Face was decent for me, mainly because we know who Dent is and all that.