I constantly back up my stuff. In fact, we had quite the system here. I would move my files to Michael's computer via the air port and his computer has an external drive that automatically backs up using Time Machine. I was so keyed in to saving my genealogy files, articles, and pictures, that I forgot some important things:
1. My address book. I lost all email addresses for everyone. An address book on a mac is not the same as Contacts on your Iphone. Those are backed up automatically if you have a me.com account, which I have.
2. My bookmarks. All gone. These can be re-created but it's a tedious and needless process.
3. My Itunes (sort of). They weren't backed up off the computer, but onto my Iphone. However to get them back on my computer I had to download a free software called Senuti (which is literally Itunes spelled backwards). That got them back on my computer.
So, those are my lessons for backing things up. I got the new computer and within one day it was all set up with all the information (minus the above) that the old one had. It was long day, but just one.