As well as the above requirements it enables you to create a bootable clone of your entire harddrive on an external drive (needs to be a firewire drive on a powerPC). This saved me no end of hassle just the other week!

I got a serious bug in my system (applications, including iCal and Safari crashing instantly on opening) that neither Drive Utily nor Drive Genius were able to repair. I re-installed OSX from the DVD and then re-booted from my cloned drive, which i knew to be clean. Whereupon i simply cloned the external copy back to the internal drive. So i was up and running again to a clean system only a week old within no time.

And if your internal harddrive should ever die on you in the field (god forbid) you can continue to run off the external cloned drive until you get a chance to replace it.

Totally worth it for the peace of mind alone imo.

That said, chronosync and superduper are great too. If you know a bit about using the Terminal, you can use rsyncx (from versiontracker) and a script like this one:

!/bin/bash

echo “Did you sudo??”

to=powerbook.$(date +%Y.%m.%d).pax

rsync—exclude-from=/Users/jlipkin/bin/exclude -v -az / /Volumes/Aleph/Powerbook > /Users/jlipkin/rsyncout_aleph.txt

This is a pretty powerful program which can do everything Retrospect can, more or less, but is harder to use.