Maybe of interest or relevant to this discussion...
DoubleCAD XT v3, is a 2D cad program that can integrate with Sketchup (and looks like other programs...or at least import and export directly to other 3D programs like Rhino).....and in doing so will retain all the 3D parametric info, and keep the objects created in the 3D app, as a block in DoubleCAD...lots of other stuff as well.
Looks like the Free version is a pretty good program that would cover the needs of most here. The full/pro version which saves and converts to a number of file types (including STL)...and has a good number of more intuitive and specialty functions is $700.
Here's a link to their home page: http://www.doublecad.com/Products/DoubleCADXTv3/tabid/1100/Default.aspx
here's a link to the Free/Pro comparison page: http://www.doublecad.com/Portals/13/new%20pdf/DoubleCADv3_compare_matrix_10-18-10.pdf
I have not tried this program, but may give it a test run (as an alternative to ACAD, for some of my work).