Well it didn't take long to hear from iPhone owners who tried the 3.1.3 firmware update to fix their existing battery problems. Some people are reporting the same problems, if not worse after updating to 3.1.3 from 3.1.2 or earlier iPhone OS versions.
Previously, many users updated to 3.1 software so they could take advantage of MMS functionality on AT&T and found that an unwelcome side effect was shortened battery life on the iPhone 3GS. (Learn how to turn on MMS without updating your 3.0 firmware here. Some have speculated this has something to do with the iPhone losing and acquiring the 3G signal repeatedly which drains the battery.
Others thought it had something to do with the processor running when it shouldn't be, also sucking the last drops of life out of the battery prematurely. Apple even had people run special software on their iPhones to determine what was causing the problem.
3.1.3 was the first update to directly address battery issues, stating that the fix "improves accuracy of reported battery level on iPhone 3GS." Unfortunately, it appears as though many users are still afflicted with the same battery problems, and others have it even worse.Users on Apple forums are reporting that their battery meter makes wild jumps from 7% to 25% and back again, and that battery life is even shorter, with only 3 or 4 hours of time before needing to charge. iPod Touch users are also reporting in another thread that smart playlist syncing is not working properly with the 3.1.3 update.
Apple has yet to make a public announcement regarding the battery issues. We're sure they are working on a solution. In the meantime, we'll await the next update from Apple and report as soon as more information is available. To maximize your battery life see this list of battery tips.