I use OpenSCAD as my primary design tool for 3D modeling. I get things done, but it isn't easy, and it's hard to recommend it to other people. OpenSCAD really requires the user to mathematics, trigonometry, mental visualization, and programming beforehand as prerequisites - unlike mainstream CAD programs which are more point-and-click friendly. Performing fillets and chamfers on corners is quite tedious, and describing a screw thread as a polyhedron is a nightmare, but I overcame these challenges.

On the plus side, I like these things about OpenSCAD:

* The software is open source, so price or pirating are not barriers, you can use it as much as you want on any computer you want for as long as you want, and it can never be taken away from you.

* The program is small and easy to download, not some multi-gigabyte sprawling software package.

* I think you learn to declare variables for parameters very early on, and it feels natural to make every design parametric from the start.

* The textual nature of 3D models means that I can use Git version control, diff between versions, and leverage similar developer-oriented tools that I use for general programming. I suspect that CAD programs that use binary file formats will have to come with their own diff tool and version control system.

* By reading source code, it's possible to follow the thought process of how a 3D model is constructed, and carefully make modifications in the middle of a chain of operations that later operations depend on. In point-and-click CAD, it's not clear to me if it's possible to change things in the middle of a chain.

* The Manifold renderer is so much faster than the old CGAL, resulting in reasonable human-interactive cycle times.

* I ended up writing my own library to cover a bunch of common shapes / use-cases. It does take some effort the first time, but then I keep reusing the results.