Re: the whole 3D discussion,
I recall seeing a comparison between the 2D and 3D blu-rays of one of the Ice Age movies. Everything was in focus on the 3D version, while the 2D had depth of field.
This is a whole lot simpler when everything's being rendered in the computer to begin with. You simply do separate renders. But when we're talking about actual photography in the real world, it's a bit more complicated.