Initial NixOS impression: honestly sucks. Installer was missing firmwares. Do you want to install the latest Firefox channel with custom prefs/policies? Too bad. Home-manager unwrapped example failed to compile. Moz overlays don't allow settings. /etc/../policies.json isn’t read.
It was neat that it 'simple' to nix-build a custom iso, but missing firmware + really old '5.4' kernel that didn't support my hardware. Not a great experience.
I still don't have a way to work with the policies.json file. Seems a lot of people want this ability because duh. There's no beta-unwrapped to use with the Wayland example on the Wiki, you can't use it with -bin or -bin-unwrapped, and it wouldn't build regardless. Cryptic error.