You're only likely to screw things up once you start digging deeper into the Nix language/stdlib. I was put off by the warning at first as well, but it's honestly awesome having functional dotfiles that work reasonably consistently across NixOS (personal)/Ubuntu (work)/MacOS (work).
> bad docs
Yeah, pretty damned awful.
> error messages
That too.
I honestly think that inventing a language was a huge mistake. Guix took a much more sensible approach, but a libre kernel is unusable for 99.9999% of people.
