There are a lot of articles about the iphone 4s battery issues. Starting at rumors about icloud draining ending at the infrared sensor which is used by siri when you raise your phone to your ear when using raise to speak. As far as I can state from my device there is a kind of phantom usage of about 1% drainage every few minutes in standby until you switch of siri completely, this has vanished after i have disabled siri as mentioned in this article here. But I do not think this is all what draines the iphones battery. The highest dropping rates come from the 3g network usage. I tried using the phone with mobile data switched off, what resulted in similar behaviour as on my iphone 4, but when you switch on mobile data you can watch the battery dropping visually. I experienced 2% in two minutes of surfing on the web, what is a not exceptable rate in comparison to my iPhone 4. So please apple follow the hints you get from your users and try to get the new comboned antenna problem right.
After a few month of using the 4s and the 5.0.1 update I am currently on an acceptable battery drain state but I was still not satisfied because my light usage caused 15-20% on my iPhone 4 already with ios5. I again scanned the threads and one thing I have not tried was the issue where you drain the battery completely, leave the device empty for at least 3 hours and then charge again. I did that yesterday. Battery was empty at about noon. I did not charge the phone for about 6 hours and then charged it to 100%. Result: average drain overnight 2%. Drain on light usage throughout the day 15%. i am currently on 1 hour usage and 20 hours standby, thats what I had before with my iPhone 4 so you should give it a try.