Hi,
I have used CAD for years. At first I thought SU was inexact but I just needed to learn how to use it--and for architectural work it's fine. Also I've seen extensive mechanical engineering work on it.
Use the measuring tape tool, protractor, snapping and inferences. There's demos on these. Try Aidanchopra.com videos.
For some things commonly done in CAD it will not be as efficient. Big thing in CAD is effective dimension and text tools. Actually spend a lot of time on that side of things for working drawings and SU is limited there.
It is not a CAD program, designed for making working drawings and such. I've seen it incorporated in a CAD workflow. But it is not a toy if you use it right for modeling. Just check out the Gallery. I've heard mention of one person trying to use exclusively SU for working drawings.
Try using in conjunction with a simple CAD 2d program that can export DXF or DWG. I actually don't know of a cheap one, or if that would be reliable enough for you.
