As with anything, "it depends." I think Nix and NixOS is great for personal and hobby stuff, but I cannot in good faith recommend it for anything professional. I personally run my daily driver on NixOS and haven't had any desire to change, but I'd prefer to never have to write an actual line of Nix code again.
> I cannot in good faith recommend it for anything professional.
What separates the professional from the 'personal and hobby stuff': the need for (timely) reliability, and that you want other people to be able to maintain it.
With Nix, because it's so strict, it's more difficult to quickly kludge a solution. If something doesn't work as you expect, it may demand understanding of different parts of the solution stack.
That Nix isn't widely adopted means it's harder to find e.g. StackOverflow answers for problems.
In the blogpost, an example of a problem they had to work around was that fish's configuration expected to work statefully in a way which didn't work well with Nix's Home Manager's declarative nature.
