I just found a great little utility to test backup systems.
It’s called Backup Bouncer and like the bouncer in a bar Backup Bouncer is there to keep the patrons honest. It will let you know ahead of time if your backup system is letting you down in complex ways, like not copying metadata or is blowing out resource forks or resetting creation dates.
These are the sorts of things you won’t notice until you’ve lost your original and for some reason your Aperture or iPhoto library won’t run properly anymore.
Of course, even a defective backup is better than none.