Are dual monitors the answer to increased office productivity? I don't know if they're such a thing as the answer, but they're certainly an answer.
They're one of those things that you don't realize how much you need dual monitors until you have tried it out. I'd tell anyone that once you go dual, you'll never go back. Some high resolution wide screen monitors where you can more easily put two windows next to each other on the same screen are close, but there's nothing like two full monitors to allow you to compare documents, using what's on one screen to write something on the other screen, or just good old multitasking (there's only so fast you can alt-tab among active windows).
I first made the jump about 7 or 8 years ago when I took an old CRT that was going to be sent to the surplus sale and hooked it up to my video card that happened to support dual monitors. It was a little awkward how the two monitors were different sizes and resolutions, but it was more productive nonetheless.
No one in the office at the time used the computers to their full ability. It was fun to watch people become interested and slowly the phenomenon spread throughout the office, until a couple years later the standard was that everyone would automatically get matching dual screens. Of course, I was in the IT department and encouraged people to order and use them. The IT department at my current job doesn't give people who work from home a second monitor and even for those in the office, according to the IT dude I talked to, IT has to approve whether or not you're worthy to receive one. It's those IT attitudes that ruin it for the IT professionals that actually care about providing technology that makes people more productive.
Maybe the answer is teaching the IT department to care. But you may have better luck just buying your own second monitor.