1. Standalone Executables: The biggest current obstacle right away! But I believe this (as in compilation to standalone, small executables) is coming with the next version (Julia 1.12) in an early form, so maybe stabilized and reliable within this year? There does seem to be a lot of momentum in this direction.
2. Vim Workflow: vim-slime works well to my knowledge, and the overall support (eg. treesitter, LSP, etc.) is pretty good, even if VS Code is the "main" supported editor.
3. Windows/Mac/Linux Support: mostly Tier 1 support [https://julialang.org/downloads/#supported_platforms]
4. Larger Imperative Ecosystem: FFI with both C and Python are pretty standard and commonly used.
5. Runtime Speed: Crazy fast as well
6. Multithreading: Base language support is already pretty good, and there's OhMyThreads.jl [1] and data chunking libraries and many other supporting libraries around multithreading.
7. Strong Community: I'd expect Julia and CL communities to be on the same order of magnitude? Complete assumption though, in both directions. Web presence is mostly on the Discourse [2] and Slack, and the JuliaCons are pretty well attended.
8. Ecosystem: Since package management is mentioned, I'll shout out the built-in Pkg package manager, the seamless virtual environment support, and the generally quite good versioning in the ecosystem, all of which add up to a really good experience. As for particular libraries, JSON is the only one I know the answer to: JSON3.jl is a solid, standard choice. I don't know if SQLite.jl [3] would be the recommended option for SQLite or something else, HTTP.jl does the job for HTTP requests but I believe isn't particularly fast or sophisticated, and I could believe there's a subcommunity within Julia that uses "functional data structures" but I wouldn't even know where to look. But, for the ex-Clojurian, may I present Transducers.jl [4] as worth a look?
[1] https://juliafolds2.github.io/OhMyThreads.jl/stable/ [2] https://discourse.julialang.org/ [3] https://github.com/JuliaDatabases/SQLite.jl [4] https://github.com/JuliaFolds2/Transducers.jl