The iPhone 4S battery can be terrible for some. It has been widely reported online that a number of users are not getting to the end of the day (or even end of business hours) without having to recharge or let their new iPhone 4S battery die.
It appears to be more of a software issue than a hardware issue as a number of users have been testing switching off the location service for setting the the time zone. It appears that iOS 5 on the 4S has a problem with regularly checking what timezone a user is in and this repeat checking of the current location is using up a lot of battery power.