Awesome program! I have a very old copy which runs on WinXP, so I'm nursing my XP laptop (3.06Ghz P4, 2GB, reasonable graphics card for that era) to keep it working.
The Tri-Ball in IronCAD is an awesome tool.
TurboCAD, DesignCAD, SoftCAD, AutoCAD, and OrCAD were the ones I dealt with most of the time for straight CAD work. Currently working on designing a personal version of a CAD program for Linux but I still need to do a lot of work on it before I can release even an alpha version for testing. Among other things, I need the specs for reading and saving to at least .dxf, .dwg, and perhaps .wmf files to begin with besides developing the program's own extension and specifications -and that is just for the 2D version.