Something interesting that I tried this week.
I have a Surface Pro 2, i5 Processor with 4 GB RAM and a Docking Station.
I installed Civil 3D 2015 on the system. I attached a secondary monitor using the docking station. I was able to run C3D fairly well for an i5 with only 4 GB.
I used the surface screen for the ribbon and prospector and the main screen to display the model.
I was able to interface with the pen and mouse fairly well. Sometimes using the pen to input directly into the ribbon. The SP2 pen is a watcomm and I think it works well for this type of interface. The SP2 has a small screen, so I think the SP3 would be even better.
I was able to move the window freely between the SP2 and the main monitor and even did some tracing of a raster image using the pen. Which was very cool.
It was an interesting experiment.