I started using AutoCAD (version 9) in 1987. Used AutoCAD extensively until about 5 years ago when I switched jobs and then started using REVIT.
I did a lot, A LOT(!!!), of AutoLisp development with AutoCAD. Mostly for my own use, then for the firm(s) I was with and some of it was even sold.
Not using AutoCAD daily for the last few years, my skills have gotten pretty rusty. But my Revit skills are better than ever.
Oh, before 1987 I used an Applicon Bravo cad workstation on a mainframe. Monochrome monitor. Stylus with a wire and a tablet (no mouse yet). One good static shock would crash the entire system, especially in the winter. Used to happen nightly. We saved often!