The article on page A24, says:
"Recent Windows and Mac computers ...can operate with multiple monitors, writes Ivan Berger in the New York Times. Once I saw how it improved my productivity, I was an instant convert....Survey after survey shows that ... adding an extra monitor will give your output a considerable booster - 20 to 30 per cent, according to a survey by Jon Peddie Research."
I have used two monitors for about 6 months now and can attest to this. In my case, I can display a dictionary on one monitor while my translation is shown on the other, or I can do Internet research on it. Also, because my new monitor is larger (17 in vs 14), I do not have to strain so much to see the text.
Another benefit is that while I use the main monitor for work, like when I write this blog, the second monitor shows my screen saver, in this particular case a view of the Marina Yatch Club in San Francisco, taken during my trip there in 2004.