One of the most fascinating things about 3D is that it expands your posibilites when you are working in field. You can literally create a set in 3D and save thousands of bucks building or renting a location. It also allows you to be more creative. One of the videos I saw in one of the blogs from last semester is the perfect example of a combination of field work, 3d and green screen. The movie is called "Nuit Blanche" and it's a movie that it's beautifully composed, and that was film entirely on a green scree. The 3d work for this short film is amazing and beyond words.
and here's the making of Nuit Blanche:
We can see in the making of that the background is mostly composed of layers of 3D objects and 2D objects. They are combined to create the world of the story. I think this is an amazing way in which we can create something innovative when are budget is limited, and the best part is that 3D helps us do that!