Thanks! And yes.. I'm against automatic updates on traditional OSs as well. If you understand how Nix works, you realize this is bulletproof!
Esp in the case here of Nixbook where the config is git controlled and I can literally test upgrades before they're enabled for other people.
Immutable + Atomic + Declarable is a pretty powerful combo.
I'm sure its not perfect, but the closest i've seen so far