WAF

Wife Acceptance Factor -- This is the measurement of how useful and stable a given installation of MythTV is: the better it works and the less you screw around with it, the more likely the non-geeky people in your life are to think it's a Pretty Neat Idea.

So, if your MythBox is "in production", and you want to hack on it, or update it, make sure you either have a second machine, or a well practiced backout plan.

See also: Girlfriend Acceptance Factor, etc.