I'm using it to unify my teams toolchain without resorting to nix or running everything in docker.
I still use docker to run services and I still like the idea of nix, but the DX of mise is too good. Tasks are really nice too, all my repo scripts now have completions.
Did you try https://devenv.sh/? It uses Nix under the hood but with an improved DX experience. I haven't used it myself personally since I find Nix good enough but I am curious if you would still choose mise over devenv.