Apple has been getting reports on their discussion boards about poor battery life from users following the iPhone 3.1
software update. These users are being contacted with plenty of questions trying to get to the bottom of the issues. Of course there are plenty of possible culprits that Apple points out – such as push e-mail, Wi-Fi, Bluetooth, and App Store apps. There's one question they ask users that's more eye opening - “When you notice a power drop, does it seem to be a legitimate power drop, or rather an issue with the battery icon indicator?” The note that Apple's help desk has been sending out to users also comes with an attachment that aims to install an unsigned profile that enables Battery Life Logging on the phone. After installing it, the iPhone will sync power logs through iTunes which will in turn be sent to Apple for further troubleshooting. In addition to poor battery life, some users report freezing issues and random shutdowns. We'll see if there's a legitimate reason to all the issues possibly stemming from the update.
via The iPhone Blog