Having checked into a number of potential solutions for the problem, I can point to this solution as being the most likely to solve the problem. We've tested this across 3 devices in the last 48 hours and it works on all 3 and has resolved all the battery issues.
Step 1 - Go to Settings - General - Reset - Reset all Settings
Follow the prompts including inserting your pin and wait for your phone to restart. This will prompt you for your pin code and will reset a number of system settings but you will not lose data in your apps or on your phone. I.e. you photo gallery will still be there. The things you will lose are your wifi settings, your photo on your home/lock screen and a number of other minor items that should be replaceable. All your apps will still be there.
Step 2 - Run your battery flat, completely flat. NOT 1%, completely flat until it actually switches off.
Step 3 - Recharge it completely, preferably for 2 hrs minimum to be on the safe side.
You do not need to set it up as a new phone and reinstall your apps or turn off LTE, Wifi and Location services as some people have suggested.
Here is a samples on the battery life after doing the above on two of the phones:
Phone 1 (light user) - Not used too much during the day. Note battery life remaining and usage. No charges occurred after unplugging.
Phone 2 (heavy user) - Used extensively during the day. Made more than 20 lengthy phone calls. Lots of email and web browsing. FaceTime calls etc.
Tests have shown that this doesn't seem to be a fault with the battery itself. There could be a small number with battery issues, but its highly likely that it's software related and with 10,000,000 phones sold in the first week, even if 0.001% had issues, that's still 10,000 of them. If it's upgrade related, I don't think Apple could have tested it on all upgrade scenarios as the secrecy surround the iPhone 5 release would limit wide scale testing of this type of scenario.
About the author
Athol Hill is the Practice Lead for Stonebridge Systems
He is a certified SAP and Project Management Professional with a large number of implementations spanning the globe including Australasia, Africa, the Middle East and Europe. When he isn't kitesurfing or spending time with his family, Athol writes part time for Mactalk on a range of subjects including iOS/OSX in the workplace, bleeding edge, product reviews and anything Mac. If you have something new and exciting to review, feel free to get in touch. He can be contacted via twitter on @themissionman