Yes, you do and should actually prepare for this update rather than aimlessly and unpreparedly going forth with the upgrade. This video will show you how you can best prepare yourself for the worst.
AppFresh - http://www.metaquark.de/appfresh/
RoaringApps - http://www.roaringapps.com/
OmniDiskSweeper - http://www.omnigroup.com/products/omnidisksweeper/
SuperDuper! - http://www.shirt-pocket.com/SuperDuper/SuperDuperDescription.html
