I'm a big fan of FreeCAD and have been using it to design and sell 3d printed parts. The learning curve was kinda steep because FreeCAD really wants you to things the "FreeCAD way" but once I got past that I started to enjoy using it.

My only gripe with FreeCAD is that the program runs on a single CPU core as far as I can tell and it's easy to lock up the program for multiple seconds if you do too complex of an operation. This isn't usually an issue for me though.