I've spent the last few years deep diving Nix / NixOS and I can definitely say that you do not want to run the unstable channel nor using flakes. Just stick with stable and if you must; add very limited unstable packages via flake configuration. Keep 99.99% on stable and do not use the latest Linux kernel either.

Using unstable will result in breaking changes giving you a headache. Trying to run a bleeding edge modern laptop with some of the absolute latest software versions is only going to blow up on you and you'll be stuck trying to work around upstream breaking changes that are not even the fault of NixOS.

Lately, I use NixOS on servers mostly without flakes and use flakes and Home Manager on Win11 WSL & macOS Darwin. However, NixOS on my laptop and workstation blew up on me with a blank black screen on every boot. There were no code changes just updating stable / unstable nixpkgs and it refused to boot. A.I. couldn't figure out what the problem was. It wasn't the video drivers; it was some kind of kernel bug with the latest kernel that bit me. I ended up with a bricked system even after burning a new ISO and wiping it out, the new installation failed in the exact same way. Trying an older kernel didn't fix it either. It would boot from flash ISO install everything, but first boot resulted in the black screen. It was eventually fixed 2-3 days later but I had a need to fix that laptop urgently.

I decided to give Omarchy a spin and was impressed; I replaced NixOS on my laptop and primary desktop workstation with Omarchy. Servers are still NixOS. While I built most things myself in NixOS, having that out of box experience with Omarchy and the fact that I can just tell the A.I. to fix and configure stuff was a game changer.

In the last year or so, A.I. has gotten much better with configuring NixOS. Omarchy provides skills.md files to train Omarchy on how to configure and fix things. This improves the overall A.I. experience on Omarchy. Without any A.I. skills the frontier A.I. agents have gotten much better at working with NixOS.

If the NixOS Community writes some skills for A.I. agents, it should vastly improve the quality of using A.I. agents to configure NixOS.

Where NixOS really shines is in solving software development problems. Writing a flake.nix file and dropping it into your repo then any users with Nix installed will execute that flake.nix via direnv when changing directories into the cloned project directory. Thus, installing all the of the project's dependencies including the language. Therefore, Node.js / Python / Ruby can be installed per project instead of per user or globally on the system. Imagine you have an old Python project that won't run with the latest Python. This is no longer a problem because when you change directories into project1 and it installs the versions you need then when you exit the project folder all the dependencies are de-referenced from the /nix/store and the environment destroyed. Change to project2 and it spins up an entirely different set of dependencies. This instantly solves many problems from a newbie developer joining the team and being immediately able to clone and build a project to ensure all the devs have the same flake.nix so they all immediately reproduce the project perfectly ensuring all the proper dependencies are working. You can also put the flake.nix in your CI / CD pipeline to ensure nightly builds are working same as the developers. Spread this across Production, QA / Test, & Development environments. You can create a custom ISO installer including your configuration in the ISO and you can PXE network boot it too. You can have a variety of computer configurations in the same Nix set of configuration files.

Nix the package manager can be installed on any Linux distribution. I am likely going to install Nix on Omarchy so I can use it for development purposes. I find Nix more robust over MISE which Omarchy depends upon for most of their development tooling.