In my opinion it's ridiculous how you have to have at least 50% battery on your iPhone to install a software update. Downloading iOS 5.1 on my iPhone over wifi took about 6 minutes, however when the update was almost done the phone dropped beneath 50% the update got cancelled. So why do you need more than 50% battery life to install an update that takes 6 minutes and drains your battery no more than 5%?! It seems to be another pointless rule, like the 50mb limit when downloading apps off wifi...