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.
Tell me about it...
The only reason I might, in the distant future, ever consider changing again is this project, which hopefully would be something between NixOS and Qubes. But that is far in the future and not even that certain.