> OpenSCAD however fails spectacularly for any kind of complex filetting situation when compared to tools like Fusion or even FreeCAD (FreeCAD's UI is an abomination though).
I've never had a problem with this, but I build up from the ground with the edges the way I want them to be. The reason many people struggle with this is that they start from 'hard' primitives such as cubes and triangles and then they want to process the edges once the rough shape is there. That's all but impossible. But you don't have to do it that way at all.
> The morphological ops in OpenSCAD (minkowski type stuff) are a very poor substitute to real fillets, and are extremely slow (underlying algos are all polynomials in number of triangles) when your objects get complex, and they are global operations, it is extremely hard to limit their action to a localized part of your object.
That's because they're used as 'after the fact' tools. It's a bit like trying to change the shape of a folded piece of metal after the fact. It's much easier to shape it right the first time than to 'fix' it later on.
When I start working on a shape like that I use a truncated cube rotated 45/45/0, place copies of that cube on the vertices of the shape I want and then cover the whole thing with a hull. Instant chamfer. If I want to use fillets I'll use a sphere. That's much easier than to first create an arrangement of cubes and other primitives and then to decide where I want the fillets to go. Picking those initial shapes for the corners is the tricky part, after that it is very quick to make (and change) objects. I've done some pretty complex shapes like this, fully parametric that would have cost me days with a traditional workflow.
> Another thing that's a real pain in OpenSCAD: you cannot "probe" (measure) your existing object at a certain stage, grab the result of that measurement and re-use it in the rest of the code. MAJOR limitation.
Yes, agreed, this kind of second order primitive is not possible. I understand the reason for it (and the reason why you can't change variables on the fly) and it is a serious drawback. This makes it very hard to relate two non-trivial shapes to each other. Interactive CAD programs are better for things like that, but there - usually - the kind of change that takes a second in OpenSCAD means a whole pile of manual work. So my recipe is to stick to OpenSCAD for those things that I think I can make with it and to use an interactive tool for everything else.
One thing that OpenSCAD excels at is remixing stuff based on existing STLs, I've yet to find another tool that allows me to do that so easily and with such versatility. Before my 'serious' cad tools have imported a mesh the OpenSCAD workflow is already printing the remixed result. As with everything: the right tool for the job is the key.