Survey after survey shows that whether you measure your productivity in facts researched, alien spaceships vaporized, or articles written, adding an extra monitor will give your output a considerable boost - 20 percent to 30 percent, according to a survey by Jon Peddie Research:

When I edit photos, the second screen lets me compare the copy I am working on with the original, or shows tool palettes and thumbnails of other images, and I can blow up panoramic shots for closer viewing (though with a bar down the middle, like the central pillar of an old car's windshield). When I am shopping on the Web, my two screens let me compare products. When I work on tables or spreadsheets, I can see all the columns at once. When I expect important messages, I keep my e-mail program open on the side monitor while I work on something else.
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Speed is one reason computer game players use multiple monitors. "If you're trying to take over the world, it's rather helpful," says Bill Blomgren, a computer consultant in Charlotte, N.C.  Video game enthusiasts use as many monitors as they can find the money and the desk space for. "Some of my hard-core gamer buddies rock three, even four, monitors for really immersive 3-D shooters," says John Walsh, a writer and reporter for the cable channel G4TV in Los Angeles.

Many games, especially those that offer a choice of camera views (including Quake and Doom), are explicitly designed for multiple screens, but the option seems most popular for Microsoft Flight Simulator. Users of that program may use separate screens for the instrument panel, maps, panoramic views ahead, views to the side, and exterior views of their virtual aircraft. (A sampling is at www.wideview.it.)

Adding monitors is just one way to gain added screen space, of course. A monitor with a 24-inch screen would offer about 50 percent more screen area than a single 19-inch model and would take up less desk space than two 19-inchers (less than two feet from side to side, versus about 33 inches for a pair of 19-inchers).