> NixOS promises stability, you just walk back to a previous version! Alas, i've had NixOS hose _all_ of my previous versions because of X server issues.

I'd love to hear more detail about this, because `nixos-rebuild switch` is not capable of causing such a problem in a permanent way.

(It can arise temporarily, though, if you switch to a new configuration without rebooting, and that configuration requires a different kernel than you are currently running. Rebooting and choosing your old configuration at the bootloader menu fixes this.)