I routinely use 3 monitors per workstation setup and this works well for my work. Each workstation has 3 computers (one each running Mac OS X, Linux, and Windows) and 3 monitors. They are configured so that each computer can use 1, 2, or all 3 monitors. In some situations, I want 1 monitor per computer, and I link the 3 OSs using Synergy. In other situations, I want 3 monitors per computer, in which case my primary monitor is in the center and secondaries are on each side. For example, I might be writing a paper on the center monitor and using the secondary monitors for such things as browsing for references, e-mailing research collaborators, doing technical drawings, carrying out statistical calculations, or posting on GH. When I am using multiple computers, one might be for routine office applications, whereas others might be carrying out computationally intensive tasks to provide input for other projects. All of this works because the graphics cards in the workstations can handle 3 or more monitors each (ATI Radeon 5870 in the Mac Pro, Nvidia GTX 680 in the Colfax, and 2 x Nvidia Quadro 2000 in the HP Z420), each monitor is switchable, and the computers are linked via both hardware (Iogear) and software (Synergy) KM switches.
Previously, each workstation had 2 monitors, but the center was the space between the two. I also tried putting one of the two in the center of the desk with one flanking monitor, but I did not like the asymmetry. I am much happier with a symmetrical setup consisting of a central monitor and two flanking monitors. The monitors are mounted on adjustable M2 Humanscale arms, so that they can be temporarily repositioned during work sessions.