I think Autodesk jumped the gun (once again) by acquiring a company and slapping the Autodesk label on the packaging. BUT, as one with years of experience using native Revit tools to build my own site models, the Site Designer tools leave much to be desired - mainly, the typical draw tools available with many of the other Revit tools. I can honestly say that if I had a better understanding of what goes into civil design, these tools may make more sense.
It seemed they were intended for Civil engineers who want to play nice with Architects in a native Revit environment. However, I found these tools to be anything but intuitive. It didn't take long to realize that the 'site' components were mass objects, so the visibility issue was short lived. I spent the better part of my morning experimenting with the site designer tools.