Not even an option in the poll for 1?
I've worked on a number of different setups, including a 5-screen battlestation at one time, but I've never been more productive than using my macbook air's screen alone :O
What I do instead is set custom triggers for every app I need to use, so from inside any other application I can press 3 keys and immediately see whatever app I want to use :D Being able to launch programs that fast makes the single screen more usable!