My battery was draining REALLY fast as well. That is what I loved most about my iP4 was the battery was a Beast. I am in Sales and the iP4 is my only phone #. No land Line, so I am on it all day with BT. I could still go into the night on a single charge most days. Not with iOS5 though. Yould watch it go down!
I started over. I did a complete "Restore AS New". No restore from back up. Yeah it was a PIT but it seems to have worked. Yestrday was much better. I let it completely drain out last night and I am charging it up now and we will see if that helps any.
I personally think it is all the Notifications that we have going on in the background. Android has the same battery problem but they brag about their notifications. Just my two cents.