Me and my customer have tested the workflow between ArcGIS Online and Civil 3D to transform gis objects in Civil 3D objects regarding pipe networks. You can´t really trust the results if you have a detail view of the sructures and pipes.
First I would like to have a better mapping between AGOL network components and Civil 3D network components. It would be great to chosse a parts list in the drawing for the mapping. This is possible but it has no effect and every time a generic parts list is generated. The user has no real control of the choosen components for pipes and structures. It would to have a mapping for the dimension and the material of pipes and the type and diameter for structures at least.
The user interface oft he mapping should be in the same way as the first new dialogue where you could already configure and save some settings in a better way.