Historically I've run arch as my main driver, however recently I've been getting into NixOS.
Immutable and declarative seem like good ideas for a setup, and overall it seems like a good thing. Don't go changing
partitions and not updating the generated /etc/fstab though cuz that's a headache. Good thing reinstalling is easy.
I use home-manager installed standalone as opposed to as a nixos/darwin module. Conceptually it seems easier to keep the system and the user setup separate, but who knows, I may change my mind about that later.