I do not own any CAD software but I have ran UnrealEd 3.0, a map editor for UT2004, on my M70. It runs very well. Smoother than my desktop rig, an A64 @ 2.25ghz with 1GB ram and a X800 Pro. I guess it is due to the Quadro being able to handle the multiple viewports. I usually run with a top, side, and front wireframe, and a textured world view without dynamic lights.
A Scratch and Dent model will usually have a problem like scratches on the lid (around the logo area) or discoloration/wear on the keyboard and palm rest region. Dent only applies to desktop tower cases. Although I would suggest waiting around until you find a certified refurbished that has been returned twice, as those recieve a larger discount than the scratch and dent machines.