Testing Draftsight before buying a license, I draw a circle with the circle tool (the units are specified as millimeters), save my file ('Circle.dxf'), and then open this file with Inkscape, a good friend of all CAM (CNC) software.

Inkscape quickly informs me that Draftsight's circle is hardly a perfect circle, and that the units that I specified (20 mm) are completely off. I then clean up and redo everything with Inkscape and wonder why I am tinkering with Draftsight to begin with. 

Draftsight has some wonderful tools (E-Snaps, for instance), but if I can't trust these tools to give me a perfect 20mm circle (diameter), why should I buy a license? Am I missing something?

Thank you for your help, anyone?