I learned CAD (formally, in a classroom) on Solidworks/AutoCAD, and once I understood the difference between part and part design, I didn't have major issues with FreeCAD-the concepts of good modeling are the same. I had some "okay, what does this software call this function" moments, but it wasn't nearly as bad as when I learned NX and couldn't find the constraints menu. I personally find the shortcomings in techdraw & assembly to be a much bigger problem than the UI-frankly, if I compare it to every engineering software I've used, it is solidly middle-of-the-pack in UI. The worst ones were commercial, expensive software. At least with FreeCAD if something is unbearably stupid I can go in and _fix_ it.