dytoractor,

IV is a parametric modeling program, whereas AutoCAD is and always will be an electronic pencil. No matter how many features and buttons AutoCAD gets, you can only draw lines, arcs, solids, etc. Every time your design changes, you will need to manually reposition or redraw every affected item, and manually ensure that your design remains within the proper criteria.

With IV, that is different. In IV, you create geometry that follows rules. If you tell two lines to be perpendicular, they will always remain perpendicular. If you give the geometry a conflicting rule, IV will tell you that both rules cannot coexist.

These rules allow you to create the design as you go, always knowing that the rules you've created in past features will hold true. Equations and interrelationships can be made that actually contain the design criteria necessary for a successful project. With AutoCAD, the engineer/designer/drafter must keep all those balls in the air at once. IV retains the intelligence of your design, so that any changes made to the design will always fall within the proper criteria.