I never thought many of the shows in on national tv were greenscreened.  From Heroes, Ugly Betty, and 24, they used green screen where you thought they never would be used.  It's amazing how good they looked.  Let's just say it's done much better than when Star Wars Episode I came out.  Stargate Studios did the work your about to see. All done in their backlot.  Truely amazing and sly at the same time.