Everything NixOS (https://nixos.org) does. I am 99% sure that if anyone tries it out and gets comfortable with it they will never change again.
- Your configuration is written in code, it is therefore persistent. Do you know that annoying feeling of "oh shit, how did I configure x program that I want to install on this other machine"? Never again.
- You can wipe your machine and recover your config in no time. I have 3 machines working with the same config except for small variations. If I change the command to take a screenshot it changes in all of them. If I change my firefox bookmarks it is persisted accross them too. Its awesome.
- NixOS generates revisions of your config automatically. Ifyou change something and it breaks you can always use a previous version of your system that you know works to fix it.
- The Nix package repository is the largest (by far) in all the linux ecosystem. And, even if a package you want is missing, adding it yourself is not that hard.
I am probably missing other nice things, but those are awesome already. It's true that the learning curve it a bit steeper than usual, but there is no distro quite like it and even for non coders you can get a lot out of it.