I also use dual monitors. Can't live without them!
I also use dual monitors, I love being able to work on two spreadsheets, etc. at one time without switching back and forth between programs
I use two - a 17" laptop and a 22" desktop. When I'm at my desk, I love having the flexibility of open apps on both, being able to create on one and do research on the other. When I'm ready to hit the road, it's easy to pick up the laptop and go. And 17" is big enough to easily work split screen, toggling between docs.
Both of us in the office here use dual monitors so we can use both screens at the same time. This is an amazing feature that I never regret adding. I can have my outlook open on one, and edit a doc from another. It saves the monotonous time of minimizing and go back and forth! :)