Definately very cool and productive with dual monitors. Even if you dont actively work in the second monitor space, it's nice to have PerfMons or Outlook running there, always within view.
Another tip: switch boxes. I also have a test server under my desk, utilizing a switch box (the brandname is "Blackbox Personal ServSwitch"), to toggle my monitor / keyboard / mouse from my PC to the test server. Really nice way to work when you do need a second computer.