Hi terrac--
Why would you want to import the isometric dwg files? If it is simply to place them on a sheet in Revit to plot, and you're not sharing your model, and your projects will remain relatively small (i.e., one or two imported dwg 'details), then OK. However, when you start to import DWG geometry, and leave it in your model permanently, the file size starts to bloat and perform poorer.
My recommendation is to create/plot sheets of DWG based geometry on the Acad/ABS side. I've heard stories of folks importing dozens of sheets worth of Acad data to create Revit sheets, just for plotting, then wondering why their Revit Systems model was slow.
HTH,
Martin Schmid, P.E.
Autodesk Consulting
Martin Schmid
Product Line Manager
Mechanical Detailing and Electrical Design
Architecture, Engineering, and Construction
Autodesk, Inc.