I upgraded my iPhone to iOS 4.3 yesterday. Sadly I made a critical error. I had encrypted my phone backup in iTunes, but somewhere along the way I forgot the password. I thought it was saved in the keychain but that didn’t seem to be the case.
Fortunately the only thing I really lost was progress in a few games and all the folders for apps. I use MobileMe for syncing my contacts and calendar so once I entered my credentials again they reappeared. Entering login details for all my apps was tedious, but using a bluetooth keyboard helped speed that up.
I do recommend you encrypt your backup; since it’s the only way to move “secrets” like Wifi passwords to a new device. However do make sure you record the encryption password somewhere safe. Otherwise you’ll have some reconfiguration to complete before your phone is ready to use again.
(Actually, I made two critical errors. I should have upgraded instead of restoring iOS.)
