This is great! The one fly in the ointment, pardon, is that Nix is a bit lax about trusting proprietary and binary-only stuff. It would be great if there were a FLOSS-only core system for NixOS which would be fully transparent.
Probably not fit for replacing Grandma's budget PC but then again grandma probably isn't worried about the ARM cross compile performance of their machine running NixOS either.
(I am worried about the ARM cross compile performance of my machine running NixOS)
Might be wrong but isn't this part of the premise for Guix/GuixSD?
But it can't do any of the things I bought my computer to do, so it's of limited value to me.