Chroma Key Backdrop ?

[rolltide]

I have been trying to come up with my own digital backdrops. This sometimes takes up alot of my time. I usually use a white backdrop and was interested in purchasing a Chroma Key Backdrop. Has anyone had experience with this type of backdrop? Is it really worth it and is time saved with it? Here are a couple with out Chroma Key.
http://www.bytephoto.com/photopost/data/500/1953columns.jpg?5139
http://www.bytephoto.com/photopost/data/500/1953planets.jpg?8993