I think its stupid that you have to always clean install an OS after every update. It makes no sense why I can't just use the back up and restore to that. So stupid!!!
1) You don't have to start clean after every OS update. Only on 2.0->3.0 and now on 4.0->5.0 you had to do a restore. Every single other OS update was just "update"able with no restore needed.
2) Even if you do a full restore, you can always still use your old backup.
What I'm getting at here is that there always seems to be some sort of issue with the way it installs or something, like with iOS 5 GM and its battery issue. Therefore you always have to do the clean install. Atleast I almost always have this issue.
My battery issue seems to be quite rare. Battery works fine till my phone gets below 50% then BOOM! Major battery drain. Had it go from 50% to 35% yesterday afternoon while it was idle.