Not suggesting nobody has a problem, but, having been around here for a whilst you might like to consider that it is quite a common phenomenon...
http://www.ipadforums.net/ipad-general-discussions/49553-ios-5-battery-draining.html
http://www.ipadforums.net/ipad-os/52386-battery-drain-performance-ios5-update.html
http://www.ipadforums.net/ipad-os/49867-battery-life-after-updating-ios5.html
http://www.ipadforums.net/ipad-os/13586-battery-ios-4-2-1-a.html
and many many more... right back to IOS 3.2.1, which was the first update for the iPad.
Personally, and from experience, I believe genuine issues related to battery after an update of IOS are caused by a panicking process caused by some flaw or bug in the update process, most likely an app, setting, or config which Apple didn't predict would be on your device and causes the new OS to "race", draining the battery.
9 times out of 10 when I have come across this before, a restore of the device in iTunes and a restore of your last backup has resolved it.
The failsafe guaranteed method to resolve it is to restore your device and set up as "new".
Good luck!