I was always told that in order to get good surfaces, you have to start with good curves!
Do some curvature analysis on your 3D curves and make sure they are smooth. Then check your surfaces. Hopefully you imposed curvature continuity where the surfaces come together. Besides the surface analysis tool you asked about earlier, you can do a quick surface check with the rendering and lighting options, and looking at the "bright spots" as you rotate the model.
While the surfaces you built with GSD can have high quality with good surface continutities, I think the Freestyle workbench provides a higher level of surface modeling capabilities.