You just described 1/2 of my working life. ( the part where I'm not doing the design work)
Although I can successfully import full 3d models from AutoCad Architect, Vectorworks, and Softplan, I find that SketcUp doesn't like the geometry they bring, and aside from the problems caused by bad draftsmanship, they are still glitchy.
I am going to try to get some of the culprits to use DoubleCAD XT, from idx http://www.doublecad.com, as from the sounds of it it may make the integration with SketchUp fairly simple,( and I like the integration between SketchUp and rendering software) while providing at least the AutoCad users with a familiar set of tools to use.
I know it has been said before, but it is interesting how there seems to be boundaries that software designers don't cross. I know that some processes seem to be under patent (hence the SketchUp shadow bug), but I keep wondering why someone isn't working on an integrated solution.