Been using duel screen monitors for years (back in the day on old crts and multiple gpu's before) made life so much easier when designing and coding websites and have never looked back.
With the costs coming down so much for monitors and most gpu's having duel outputs these days sure more will run duel screen or more over time, as most have already said has so many uses when multi-tasking running a game on one while everything else is running on the second (vent,web,etc) don't think I could go back to one screen.
Would love the Samsung MD230X3 or MD230X6 Widescreen LCD Eyefinity Monitor setup if the money wasn't a problem, one day maybe