I did. With the Sonar X series, with the dock and screensets , I don't really see a need for more than one screen.
I got tired of needing to turn my head to concentrate on what I was doing. I find it more comfortable working for long periods looking straight ahead.
I did add a touch screen but I mounted it below my main monitor slanted like a control surface. The touch screen is the only screen that I use when working in Sonar.
Sometimes I leave the GUI for my audio interface on the upper screen while tracking just to keep an eye on levels coming into my audio interface.