Back when I tried it, it felt more like an advanced calculator with a text interface than a "magical calculating plaintext file" to me, which is what I want. But lots of people love it.
The other option is something like a Jupyter notebook, or perhaps a Swift playground. But those are not nearly as easy to set up and use.
Just for fun, here's my most recent Calca file. The numbers after "=>" are calculated by the app. Note that it understands (and converts) units of measurement.
