I think the point is, there is no more dependency hell.

Exactly. Using both in production, zero dependency hell. yum and dnf are great.

You're missing out. Nix is a fantastic package manager with features that apt (and similar) simply do not have. NixOS is not perfect yet, but it's very usable, and quickly improving.

Can't say this enough. You write a config script for your OS and run it.

Need to set up device #25?

Upload and run. You're guaranteed to get the same system as device #24,23...

You can keep it in source control, etc.

If it (or guix - no systemd FTW) takes off, I can't imagine using another distro again.

Unfortunately, though, it doesn't have enough maintainers yet (a year or so ago nginx was some 4 or 5 versions behind, and they definitely don't do backports/LTS).

The biggest problem Nix[OS] has right now is documentation. The wiki is deprecated, but still the only source for explanation of several key parts of the system. nix-shell is fantastic, but hard to learn simply because there is no specific place to learn. Nix language really needs some clear documentation so a user can understand how to get from "I don't have X" to "I have a working default.nix for X, and X installed in my environment."

GuixSD seems nice, but seems to have no method for installing non-free software, which is, unfortunately, necessary for many setups.

One thing I would like to have is a Nix/Guix wrapper for Debian packages (and possibly other packages/distros), so I could take advantage of Debian's robust ecosystem, and NixOS/GuixSD's totally functional environment.

My problem with documentation isn't so much that the nix language is so hard, but that a nix's package configuration's is (obviously) not the same as upstream.