We have had a Scene Machine for many years, used to use it a lot, but for the past years have given it up. Since we are all digital, we have started to use it again, I must say that digital cameras and the ability to review the shot on the camera's display has really improved the thing.
Before you give up on the idea, look at the work of Joseph & Louise Simone, their web site is Louise et Joseph Simone, portraitistes
They have taken this technology to new heights. There are other innovative photographers taking advantage of this and you can see soem of their work at Welcome to Virtual Backgrounds
We also to the "green screen" effect, but use Corel Knock Out to remove the backgrounds, we shoot the portraits on white seamless vinyl backgrounds. The Knock Out's are very accurate, and fast to do, by using white, we avoid the green edges we always got with green screen.
There is great potential in being able to use all kinds of backgrounds, especially local scenes, in the efficiency and comport of my own studio.
You can see another way we are doing this with large photo prints for backgrounds, at this page in our web site: Senior Portraits