I've a lot more experience with Julia than any other language (and am a huge fan/am heavily invested). My #2 is R, which has a much more basic type system than Julia.
So -- as I don't have experience with languages with much richer type systems like Rust or Haskell -- it's hard to imagine what's missing, or conceive of tools other than a hammer.
Mind elaborating (or pointing me to a post or article explaining the point)?
I found multiple dispatch to be odd at first, but after adapting my mindset a bit I really like it. It makes it really easy to just drop your functions specialized for your types into existing libraries, for example. It's a win for code reuse.
What do you mean by "types are too shallow"?
Yes, jit can be slow to boot, but I think this is an area they're going to be focusing on.
"the tooling is poor" Not sure I agree here. I think it's great that I can easily see various stages from LLVM IR to x86 asm of a function if I want to.
Boot times still aren't ideal, but I find it takes about .1 seconds to launch a julia repl now. First time to plot is still a bit painful due to JIT overhead, but that's coming down very aggressively (there will be a big improvement in 1.5, the next release with differential compilation levels for different modules), and we now have PackageCompiler.jl for bundling packages into your Sysimage so they don't need to be recompiled every time to you reboot julia.
I also think the tooling is quite strong, we have ana amazingly powerful type system and I would classify discovering multiple dispatch as a religious experience.
