We use it for OCaml because there’s nothing in OCaml that really exist to manage dependencies and build (opam and dune are awful). But it doesn’t work well with our Rust dependency. I think it could work well with our Rust dependencies (which needs to be packaged with a derivation and thus doesn’t work in a nix develop shell) if nix stops where Cargo begins, but it seems like it is not nix’s philosophy.