Also, my Mac is 256gb which feels far too cramped for Nix. I'd really only recommend it if you're working with 512gb or more.
home-manager works better than I'd expect. At least I don't have to spend time configuring vim, git and shell prompt.
But overall, Nix on MacOS feels like a hack, behaves like a hack... because it's essentially a hack...
I'm waiting for the first reports of Lenovo's t14s gen 6 with Snapdragon X Elite.
If that's really all you use it for, and you already use Home Manager, the Homebrew module for Nix-Darwin works fine in Home Manager with some small tweaks. I use that with a custom, per-user Homebrew prefix to keep Homebrew out of the way except for the task of installing casks.