Hello,
Check out this thread I started on dual monitors:
http://forum.datacad.com/viewtopic.php?t=43
A correction on what Greg said: you can span the monitors with the drawing window. On the third example (in the linked thread), I have two drawings visible in the drawing window, and the divide between the two monitors is at the boundary between the two drawings.
On all the other examples, the dividing line is at the right edge of the main menu, which is still docked i nthe main drawing window.
At my office, I actually have
three monitors, at this moment. I use two for DataCAD, and the third (smallest) one I use for whatever else I need to have there: a SketchUp model for reference, IrfanView showing a photo for reference, a browser window, Skype, WinAmp, etc.