Couple of things to think about...
IF you draw in 3d, you will need to export from VW in a 3d mode/view... (5 on the numpad is 3d Plan, 0 on the numpad is 2d Plan) VW will not export both 2d and 3d portions of symbols to autocad. So if you're in a 3d view, it will export the 3d data, if in a 2d view, etc...
On my Export options, I only select "classes" and "exported as invisible layers" I UNSELECT EVERYTHING else... that works the best with autocad. I would never want to rescale layers, and you can decide whether or not you need hatches or images, mapping line weights always seems to be a nightmare...
anyway, hope that helps a little.
Vectorworks 2009 Designer / Renderworks
Windows XP Pro SP3
Dell Precision WorkStation T3400
Intel Core2 Quad CPU 2.66GHz (4 CPUs)
3326MB RAM (4GB)
NVIDIA Quadro FX 3700 512.0 MB