On rare occasions, there can be problems restarting a service, like if the service in the new configuration in fact relies on a newer kernel module than what yo

On rare occasions, there can be problems restarting a service, like if the service in the new configuration in fact relies on a newer kernel module than what you've got in your running configuration. In addition, sometimes Nix's garbage collector won't dispose of something because it can tell you've still got some processes running that use it or something like that, and so there's a bit of space you can't free up until after reboot. And of course, kernel changes still require reboots on NixOS. All in all, the service management stuff is handled very gracefully imo. I've never run into real trouble with it (and one time I had a power outage in the middle of a `nixos-rebuild switch`).