In my experience there are still some rough edges as compared to the Python ecosystem (of course!), which together with the 0.x status make it impractical for many production situations. However it is fantastic for prototyping numerical code, the type system is a pleasure, and the JuMP mathematical optimization library is a gem. Being able to have fast code be "first class," as opposed to the impedance mismatch of dealing with numba/Cython, feels great and is a real boon for trying new things. Then, it is fairly straightforward to port the final solution to whatever production language you use (e.g., Python with a sprinkle of numba).