I also think there is something to be said for the quality of code available for Julia, aside from just the quantity. DifferentialEquations, JuMP, Flux all seem to go beyond what is available or even possible in other languages in a significant way. There are also some cool tools available such as StaticArrays, RigidBodyDynamics, Query which are certainly possible in other languages (and indeed have many other implementations) but have impressively straight-forward and succinct code in Julia. Lastly, a lot of the “core ecosystem” stuff like DataFrames, JuliaDB (which I expect to take on a larger role after 0.7) are starting to look pretty slick and offer some flexibility that is hard to come by in other languages.
10 years ago if you had shown me this stuff, I would have been blown away. Suffice it to say that’s very different from the puzzled reaction I had when I first saw Python.