I currently use a Matrox Millenium G550 with a pair of Philips 107S4's. I like having the two screns, and believe that productivity is increased by not having to switch between documents.
Now the bad bits - All system windows appear centered between the two screens making it hard to read them. With the DVD Max feature, the video is supposed to appear in the second display. Fair enough and it does a good job. But is stays there when the initial window is closed, overriding everything including the taskbar.
Generally though, two monitors seem better than one. I have more problems with Arcview crashing than I do with the monitors.