>Have you, or anyone, ever lived with such a system?

Yes, I live with a few of them, actually, just not computer related.

The power delivery in my house is a capabilities based system. I can plug any old hand-made lamp from a garage sale in, and know it won't burn down my house by overloading the wires in the wall. Every outlet has a capability, and it's easy peasy to use.

Another capability based system I use is cash, the not so mighty US Dollar. If I want to hand you $10 for the above mentioned lamp at your garage sale, I don't risk also giving away the title to my house, or all of my bank balance, etc... the most I can lose is the $10 capability. (It's all about the Hamilton's Baby)

The system you describe, with all the needless questions, isn't capabilities, it's permission flags, and horrible. We ALL hate them.

As for usable capabilities, if Raymond Chen and his team at Microsoft chose to do so, they could implement a Win32 compatible set of powerboxes to replace/augment/shim the standard file open/save system supplied dialogs. This would then allow you to run standard Win32 GUI programs without further modifications to the code, or changing the way the programs work.

Someone more fluent in C/C++ than me could do the same with Genode for Linux GUI programs.

I have no idea what a capabilities based command line would look like. EROS and KeyKOS did it, though... perhaps it would be something like the command lines in mainframes.