I have been using two monitors on my desktop computers for years. I love the convenience of displaying my email program, a web browser, iTunes, and RSS newsreader displayed on the monitor to the left side of my desk while my word processor and my favorite genealogy programs are running in separate windows on the monitor to the right. Doing so is a time saver, and I believe it improves productivity significantly.
I especially like to display two different genealogy programs simultaneously, one on each monitor. That makes it easy to compare two different databases and even to copy-and-paste information from one program to another.
Not only can I display different programs on different monitors, I can also move any window from one monitor to the other. You know how you can click-and-drag a window from one area on your single screen to another? I can do the same with two monitors: click-and-drag any window from an area on one monitor to an area on another monitor.
I can even create a really large Excel spreadsheet that spans both screens, showing hundreds of “cells” simultaneously. That is usually an eye-popping demonstration as many people don’t realize that this is possible. It is easy to have the one spreadsheet or image spread across two screens: the left side of the spreadsheet or image can be displayed on the left monitor while the right side of that spreadsheet can simultaneously be displayed on the right monitor.
Having 3 or more screens is also great for Flight Simulator! Your computer screens will look like the cockpit of a Boeing 787!