Several iPhone users who have updated to iPhone 3.1 have posted on the Apple discussion board concerns on poor battery life since upgrading to iPhone 3.1 and as a result they are being contacted by AppleCare helpdesk with a list of 11 follow-up questions reports the iphone blog.
Apparently the questions primarily focus upon WiFi, email, App Store applications, Bluetooth and question 10 asks when noticed does the drop appear to be a legitimate power drop or an issue with the battery icon indicator.
There is also an attachment in the note that when double clicked install an unsigned profile and once enabled will sync the iPhone power logs back via iTunes which Apple asks you send back to them. So it looks like Apple is looking into these battery problems.