Perhaps it's a borderline case, but I've used Julia to make a "big data" database server, backed by a mmap'ed column store.

Because the compiler's available at run-time, queries can be compiled into efficient kernels that can run in parallel over multi-gigabyte arrays orders of magnitude faster than MySQL or Postgres on the same hardware.

Without Julia, I would have had to find some other way to compile queries into machine code at run-time, which for me would have ruled out all the languages you listed. In practical terms I would have abandoned the project.

Excellent use case.

>Without Julia, I would have had to find some other way to compile queries into machine code at run-time

Note that you could also do it in Common Lisp.

But I agree, Julia is very powerful, perhaps one of the most powerful recent languages.

For the most part, no. The language and community are significantly math oriented. However, if you're someone who likes to learn languages just to broaden their horizons a little bit, Julia might be a good choice. It's one of the few languages in common use which has multimethods (the other major one being Common Lisp). Actually, in general Julia is surprisingly Lispy for a language with Algol-family syntax.

> Actually, in general Julia is surprisingly Lispy for a language with Algol-family syntax.

It's less surprising if you know there's still a version of the Julia REPL that works with sexpressions: https://youtu.be/dK3zRXhrFZY?t=5m58s

I use Julia for shell scripting. Remember how many ende up using ruby for this? Well Julia works even better. I don’t write big programs in Julia. It is just a kind of everyday tool. I am a C++/Swift/Objective-C developer professionally.