We switched to using Nix at our startup because the rebuild time, reproducibility, and performance of Docker (especially on MacOS) were really slowing us down. Building and starting our dev container could take several minutes if we busted Docker's layer cache, but with Nix we never had to worry about that.

We open sourced our Nix dev environment tool (Devbox), and wrote a bit about why we switched here: https://www.jetpack.io/blog/devbox-turn-a-1000-container-scr...