Time Machine

Everything you ever wanted to know, or perhaps more than you wanted, about Time Machine. Super in-depth review and technical behind the scenes report of how Time Machine does what it does. 9347 words by Sven-S. Porst. If you find the tech stuff a little much you should skip down to the "Restoring Files' section and read to the end. Lots of criticism, some deserved, but the bottom line?

Time Machine is worth having because it does make an additional copy of your data and is unlikely to accidentally destroy that additional copy.