I learned Octave from the Andrew Ng ML MOOC and since then, I like to use it occasionally as an advanced calculator. It's pretty handy to quickly run on the command line and play around with some ideas, but for anything that involves more than a throwaway script I'd most likely switch to a more "serious" language.

What I will say is that I really enjoy using Octave, just because with a certain fairly narrow domain it's quick, powerful and there's no messing around with dependencies to get going. It's very immediate, which is exactly what I want from a calculator.