Bob,
I like you have been hunting high and low for a good useable cad system that interfaces well with SU. I have splashed out and purchased SPIRIT. I am still trying to find time to come to grips with this programme, I have never been cad literate, just pen and pencil literate from the old school. The nice thing about SPIRIT is that you can reference a SU model back in to SPIRIT including all components. You can then change the model in SU and it updates in SPIRIT where you can create either 2D plans / drawings or 3D parametric models. We use Revit in the office as well but from what I have seen ....and I am no expert as I don't use Revit either.....it is just as capable. It might not be able to handle larger more complex projects like Revit can I suspect. The work flow suits me as I enjoy working concepts up in SU and then having the ability to produce some good looking preliminary design drawings is all I need. I employ staff to do the detail design and documentation.
I would love to be able to show some drawings I have produced in SPIRIT from an SU model but I haven't got that far yet, all my spare time at the moment is taken up up pulling in work.

Stan