I've been using NixOS for about 2 years now. I use it on my main PC, and it's been the best linux distro so far.
It's package manager is probably the best part. I have access to the biggest repository of apps, all of which are built from source and are reproducible. I can also create my own packages stupidly easily.
I've used it in production to create and deploy minimal docker containers. The fact that I can turn my apps binary into a baseless docker image with basically 0 effort seems like dark magic.