Does a Dual/Multiple Monitor Setup Increase Productivity?

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Awhile back, the New York Times published an article that claims that a dual monitor setup increases productivity.  The idea is that more desktop real estate results in multitasking that can get more things done.  On the flip side, too much multitasking (especially when distractions are included) could lead to less productivity.

Personally, I prefer a dual monitor setup.  I went from having three 17 inch monitors to a single 24 inch and now two 24's.

Does anyone else run a dual/multiple monitor setup?