I just configured my computer at work for dual displays. Several of the other guys have dual displays with 19" LCD's, but I haven't convinced the company to buy that setup for me yet.
Recently my wife had wanted dual monitors for the checkout computer in her store, so I bought an Nvidia-based video card on sale at CompUSA. Of course then she decided she didn't really want the dual monitors so I had this video card just setting here.
Then 2 days ago another guy at work got a new LCD monitor and put his 19" CRT in the storeroom. So I brought the spare video card from home, put it in my computer, set his old 19" CRT beside my old 19" CRT, and cranked it up. It's pretty neat but somewhat hard to get used to.
We run CAD and some other applications that need to share data, so it is convenient to have CAD open on one screen and the other app open on the other screen. Much more convenient that having to switch back and forth. Sure, with one screen you can go to the taskbar to switch apps, or CTRL-TAB, but for some reason it seems to throw a break into the thought process and that interruption hurts productivity much more than it would sound like.