I use 4 monitors (1600x1200 20") and it helps quite a bit with the kind of work I do. I work with many VS solutions and often average about 7-14 open at a time depending on what I'm doing (right now I have 11), often debugging between 2 or so. I also typically devote 1 screen to a big log window or testing apps, 1 to docs / web browsing / email, and 1 to system monitors and a MindManager map with hyperlinks to quickly navigate everything (I have 20+ solutions total (each with many projects), and digging thru directory trees in Explorer got old.) The 4th helps but I have mainly have it because it was just sitting around (and because it helps my tan), but having less than 3 would slow me down in my job. When I'm coding elsewhere with only one solution at a time, working with 1 monitor is often fine, although it's nice to have a 2nd.