I posted how I stopped the battery usage drain on my recent iPhone 5 16GB purchase using iOS 6.0.2 on another thread here on Apple's support forum:
I have created a new thread since reading through 67 pages of complaints and partial solutions might consume too much time for some folks:
Dec 29, 2012 5:07 PM (in response to mhabashy)
I'VE SOLVED THE BATTERY DRAIN PROBLEM On My iPhone 5 iOS 6.0.2!
I just got my iPhone 5 this week (Dec 23, 2012) after deciding to use a customer appreciation email from the president of Rogers Wireless Network stating all fees would be waived (including upgrade) plus he would include a $100 Shopping Channel gift credit! I got to the store and discovered there was a further $50 rebate, which means I made $10.23.
BATTERY DRAIN PROBLEM & RESOLUTION:
I got the iPhone 5 16GB. I used iTunes to restore all my Apps and files. I noticed a battery drian that was way out of whack! (along with something else) I erased all content and settings then restored with iCloud. Same thing, no change. I did all sorts of stuff to figure out who was the culprit. I have narrowed it down to removing all Gmail accounts from Mail. My gmail accounts were the only emails that would fetch. All the others would have data pushed. My settings for notifications, brightness strength were set to normal and I used GPS to locate a coyote in town, along with 2+ hours constant internet use at doctors' office, etc, etc. The battery drain was similar to what my iPhone 4 would have used, possibly even less, even though it needs more energy to power the larger screen.
Whether Gmail is the culprit or the fetch feature, I don't know, but the fetch and gmail on my iPhone4 with iOS 6.0.1 is not an issue.
Other issues that I am aware of with the iPhone 5 using iOS 6.0.2 is the fact that sometimes it will not charge when plugged into the computer USB port and even the 120V wall outlet. I would have to unplug and replug it in.
PS: WOW, is this LTE FAST! I've clocked download speeds of 37Mbps, and upload at 29Mbps via www.speedtest.net.
iPhone 5, iOS 6.0.2
There are replies to my original post that you might want to read.