Computer-aided design (CAD) is another particular application for 2D vector graphics. A difference between CAD and other types of drawing is that precision is extremely important. Another difference is the need for dimensioning of items in the drawing. Workflow can also be very different between CAD and other vector drawing uses. Because of these reasons, Inkscape is unlikely to ever be useful as a CAD tool directly.
However, being able to import CAD drawings for final cleanup/rendering, or to mock up some ideas before putting into CAD, may be of use. The de factor standard exchange format for CAD programs is DXF. Having support for this format suddenly opens up interoperability with a huge range of other applications, including not only 2D CAD such as qcad, but also 3D rendering programs such as Blender, etc.
A nice workaround to import cad drawings in Inkscape could be the following: 1. create a pdf via pdf creator (gpl'ed - windows) or via any other distiller 2. open it Gsview and use the command "convert to vector format" via GnuLibplot to convert it in SVG format. 3. the file is ready for Inkscape.
As an alternative, you can use the command line for pstoedit or GnuLibplot, but they are much more tricky to install under windows.