I remember how awesome it was to switch from Homebrew to Nix, noticeably the speed. But there is something off about Nix: + Installation process, especially on Mac: nix, and then home-manager. And I don't even mention flake. Right now I'm settled with a helpful script from https://nix.dev/, but I don't say I'm fully confident. + How to add an external package which is not in nixpkgs. I have to learn Nix and dig Nix docs and ask too many questions to figure this process. In the end it is awesome but I could feel the barrier for beginner. + Documentation. It's easy to get started with some popular packages but it's a pain to customize your own. I always find myself banging my head to dig the information I need.

So in conclusion, Nix is awesome to use if you invest time to learn the Nix expression language. Otherwise you have to stuck with the default packages provided by nixpkgs.