There was a study done on this a while ago: http://www.npr.org/templates/story/story.php?storyId=89140287 http://www.npr.org/templates/story/story.php?storyId=8

There was a study done on this a while ago: http://www.npr.org/templates/story/story.php?storyId=89140287 http://www.npr.org/templates/story/story.php?storyId=8914028... I agree with the premise that there are diminishing returns after the 2nd screen, but I personally always use my 13" Macbook screen alongside the cinema display when I'm at my desk.