No Kidding!! Most of them work the same just different looking buttons and commands are often applied in a different order....which can be hard to keep straight in the old brain.All of the ones I learned on will actually shut down and not work if they haven't been paid for. My favorite was Inventor which is a 3d parametric software. The last free software I had was DraftSight which is made by Solidworks, but they discontinued the free 2d software to focus on the paid 3d software. So now I am learning Free CAD which seems to do everything but I have to figure out where all of the buttons are.
I bought Inventor and Mechanical 2011, to start freelance biz after losing 18 year job.
Freelance was same work but 1099 thru machine shop instead of tech staff leasing, long story.
Didn't use much 3d at job(Microstation didn't have a good one)tho I pushed for it,
but went back to school and learned Inventor, Solidworks, and Pro-E....chose the Acad suite.
Have played with a few of the 'free' programs, most notably Sketch-up,
but frankly was burned out on 'learning another new software'.
So I still have the full programs on hard drive, but don't do much designing the last few years.