[cubicle67]

I spent a few years working for BigCo, and the one thing I learned there was an appreciation for rollback scripts.

every single change had to be accompanied by a full and tested rollback script, and given often the deployment was messy (lots of integration/hardware mixes/etc) writing these was difficult and time consuming. ... but, they saved my arse on more than on occasion.

moral of the story: always have a backout plan. Stuff goes wrong. not often, and if you're good, then rarely, but when it does you need a way out.