@technomancy That's a great question. This is what I answer any time someone asks me a something I don't have a good answer for.
I think that something like the Guix/Nix model has a lot of interesting possibilities. Like: my current setup *works*, but is kind of a mess -- a customized Debian installer, thousands of lines of Ansible junk, a 100+mb dotfiles repo. Things are sort of reproduceable (I can set up another machine like my current one), but involve a *lot* of manual work to do. I like the idea of all that complexity being managed natively by one tool built into the OS.
I like the idea of having a strong system-level package manager (that is, more sophisticated than a Slackware-like "unzip this tarball in /" model) which can also cope with the various weirdware I use that don't justify a package anywhere else.
I like the idea of using Scheme for all my configuration.
I like the idea of interacting with the OS abstractions through Emacs (which you can do with emacs-guix).
It's genuinely nice to, when you need some software right now that you'll probably never use again, to run `guix shell name-of-package` and use it and close the shell and not think about it ever again / not have it hanging around the system.
I like the idea of never having to deal with nvm/rbenv/pyenv/virtualenvs ever again, because I can create a profile with the correct versions of everything I need. And if a different thing needs different versions, I can make a profile for that, too.
I like the idea of never having to resort to Flatpak/Snap/AppImage trash, because anything can be reasonably made into a native package.
Most other distros don't do *any* of these, much less all. NixOS is the only one that comes close (because Guix is based on it).