Batterygate is real folks.
I have tried literally everything suggested in this thread, including the dreaded restore, erasing everything. I had hopes last night that it was fixed when I saw my phone stay at 100% for a few minutes after unplugging.
Overnight Usage Times:
Wife's Non-Affected Identical iPhone 4S: 94% after 10.5 hrs off charge, all in standby. If you do the math, that equates to close to the advertised 200-hr standby.
My iPhone 4S: 67% after 4.5 hrs off charge, all in standby.
My 8-month old son woke me up at 4:30am. I had taken mine off of charge at midnight following the restore. Imagine my horror to see 67% as the battery left when I checked it.
I'm done. I'm going to the Apple store and demanding a new one. There HAS to be a manufacturing defect with mine, and I wouldn't be surprised if a lot of folks have a battery lemon like mine.