The last few years have seen drastic improvements in green-screen technology.
Notice how that the actual screen only needs to cover the moving objects in the scene; that’s the part the computers still have trouble with.
With the way things are going now, I suspect the need for an actual green-screen will disappear within ten-years; we will soon be able to design programs that will be able to “cut-around’ the objects we want them to. These programs already exist, but are imperfect.
EXTRA THOUGHT: Lighting was the major issue that kept green-screen from total realism for so long; the difference between the lighting in the scene and the lighting on the green-screen set gave it away. Pretty recently, light editing become much more powerful (thanks in part to Lucas.) The coloring and light on a persons face can now be changed well after the shot (professionals usually try to adjust all the elements in the shot to each other.)
EXTRA EXTRA THOUGHT: When a special effect looks wrong, it’s usually because of a disparity between the textures and lighting of the different elements of a scene (motion difference plays a part in this as well, but animators have gotten a great deal better at this in recent years.)