Nandroid is a perfect backup tool !! esp. for those who crave to try new ROMs. I'm on Defy and every week, I try a new build of ICS ROM from various people. All I need to do is to backup my MIUI 2.4.20 ROM and flash the new ROM. If the new ROM has problems, it hardly takes 10 min to get my phone to its previous state !!
Hit Thanks if it helps !