I use NixOS BTW.
Since switching to it on all of my servers, my quality of life has somewhat improved - check out my last blog post about Hosting Websites on NixOS. I am also now of the opinion that hosting your own mail server is the sensible thing to do, as it's now just a few lines of configuration and it works rather well. Prove me wrong.
Now also on the desktop
I liked the declarative nature of Nix so much that I decided to go all the way in and also switch to NixOS on the desktop. The transition was rather painless. NixOS even provides a graphical installer and KDE plasma is very well integrated from the get-go.
Using it, I must admit that Arch Linux, my previous daily driver and the undisputed king of Linux memes, feels rather antiquated in comparison. There's no more clutter-prone package management, no more fear that a system upgrade might go south and consume a few hours of my time. Now I can switch desktop environments in a matter of seconds, declaratively create systemd services for all of my boxes at once, and roll-back configuration at boot time. The icing on the cake is the vast amount of packages available in the nix repository that rivals that of the Arch user repository.
Well that's me. The whole NixOS on the Desktop thing may not be for everyone, but knowing what I know now, putting it on the server should be a no-brainer.