iOS 6.1.3 was meant to fix the screen bypass bug — which it only partially managed — and enhance Apple's Japanese maps, as well as subtly killing jailbreaking. Instead, it appears that it may be recreating what's been a common bug in iOS updates, sucking precious battery life away as well.
That's probably not an intended feature, now that I think about it. A number of iPhone users report hitting the bug after installing the app update, with many throwing around fixes relating to changing email account or iCloud settings to possibly fix the bug.
Battery life issues are the pits, but they can also be highly subjective kinds of things, depending on your exact app configuration and the age of the battery itself. Any Giz users hit notably bad battery life after installing iOS 6.1.3? [CultOfMac]