True, it's not a full replacement for ipmi-ish tech. There are ways the deployed waiter can fail before it times out and triggers the rollback. Deploy often enough and you will hit all wonderful edge cases. I treat it as a first line of defense that saves me time on scooting the chair over to me server cabinet and yanking the cords.

WRT ephemeral state -- NixOS allows to minimize this. Coupled with impermanence, all non-declared and non-externally-retrievable state is wiped away upon reboot. And if it's not declative and not retrievable, I just don't use it. Homelab allows for a lot of choice in that regard