"What change are you talking about? Not much has changed in the basic geometry handling of AutoCAD..."

I'm actually asking about the changes that allow other programs to do things like parametrics and dynamic re-assignment of the drawing plane that AutoCad can't do. It just seems to me that they are stuck with some core functionality that they can't really improve on in an efficient manner, so they end up buying newer companies in order to keep up with the competition. I'm guessing that the way the math is handled at the base level is what they are stuck with and if they changed that they would break everything else.

I teach AutoCad, Inventor, Revit and Sketchup at the technical college level. (I got interested in Moi in order to learn about nurbs based modeling in case students start asking about it. Everybody wants to be a car designer!) AutoCad has reached the point where they continue to change the interface year after year without actually improving the efficiency. I wish they would just leave it alone, but that doesn't sell new copies of the software.