NixOS is the only[1] Linux distribution that feels like it is build around Free Software. Meaning upstream Git repositories can be treated as first-class citizen and installed directly without convoluted binary packaging system (that still exists in the background, but only as cache to speed up build times). Nix also makes it very easy to upgrade, downgrade, side grade, patch, override dependencies or otherwise change packages, or even just keep multiple versions of the same software around. Something many other distributions still struggle with or make completely impossible with the distributions own tools. Even the act of installing software in Nix becomes somewhat unnecessary, as you can just run software straight from the Git repository.

And best of all, it’s all based on a very simple and transparent packaging system, if you ever used GNU stow, kind of like that, it’s all held together with a bunch of symlinks and some environment variables. No contains, no ostree, none of those ugly workarounds, just plain old Unix stuff that you can find and grep through as much as you like.

Simply put, NixOS puts the joy back in Linux, while other distributions like Ubuntu try to actively trash their reputation with a proprietary App store and others like Debian just stagnate around and are still stuck with the same old packing system that was state of the art 25 years ago and hasn’t improve much at all since than. NixOS just provides a dramatically cleaner and simpler approach that also happens to be vastly more powerful.

Another cool thing, if you don’t wanna switch distributions just yet and reinstall the full NixOS, you can just use the Nix package manager itself on whatever distribution you are already using.

As for downsides: Nix does not play nicely with packages, scripts and programs made for other distributions, like at all. /usr/bin/env and /bin/sh are about the only files it has in common with other distributions, the whole standard Linux file tree is completely empty otherwise. There is buildFHSUserEnv to work around that, but that requires a bit more knowledge and effort from the user.

[1] There is also GNU Guix, which is basically a reimplementation of Nix with Guile/Scheme