I tried out nixos (the complete distro based on nix) on the weekend -- it's not saying too much that it's a revelation. I can see myself completely switching for my development machines and possibly for servers as well.
The amazing thing is that the whole set up of your linux machine is encaptulated in one declarative text file (that you can put in version control). Give it a try by installing it using VirtualBox: https://nixos.org/wiki/Installing_NixOS_in_a_VirtualBox_gues.... You can log in (demo/demo in the 14.10 vm) and play around, essentially be editing `/etc/nixos/configuration.nix`.
I recommend trying the configuration of an experienced user. Here's the result of a simple search on github:
Reminds me of archlinux early days when one of their main arguments was that configuration was done in a single file (as BSDs). Nix is like a typechecked version of that.