I literally took my phone off the charger about 10 minutes ago to update my rss feeds which took about 30 seconds, and browsed through them and found a link about the iPhone 4s and the terrible battery life. Just in that time my battery had already dipped to 96%.
SInce I first receive the phone, I noticed the battery issues. Being that I came from the iPhone 4 which had amazing battery life, the iPhone 4s is just terrible. I have followed many of the battery related fixes (ie turned off location based apps in settings, dim back light, fetch mail manually, etc). I have run tests at night where I charge completely to 100%, reboot the phone (to make sure no programs are running in the back ground) and let the phone sit untouch over night, and after 6 hours the phone would be down by 17 - 25%. I did this test several times on different iPhone 4s' (3 of them), so I know it was not just one bad phone. I did notice that the phones with the blue color screen (my preference for display) seem to have slightly lower battery performance than the yellow screens (which I can't stand to look at), but this may have just been noise in my testing results.
After enabling and disabling different features of the phone, disabling the cellular data made the biggest difference. Running the phone with everything enabled except iCloud and cellular data, my phone was able to only loose 7% over night. It seems strange to me that when I have wifi enabled and cellular data turned on, that it would drain the battery that much extra since all data should be going through WiFi anyway, but based on that test, even if wifi is on and connected, it appears that cellular data is still active. Has anyone else seen this?