Posting here for the first time. Everything was great on 2.3.4, could squeeze two days out of it with moderate/little use. After the OTA upgrade to 2.3.6 yesterday (Jan. 16), battery life is horrible, and I do see that the Android OS is gobbling up most of it, like others have posted. I have a couple of questions/observations:
1) When wifi is ON: I noticed that when I touch the screen with the back of my palm close to my thumb (to get most sensitivity to temperature), it is somewhat warm in the upper middle, close to the AT&T logo. Is this where the WiFi card is located? Is this an indication that something is wrong with it if it's heating up so much? Can someone point it out to the guys at AT&T and/or Samsung? You can feel the screen in different spots, and there is a noticeable increase in temp. in the upper part. (If you have your phone in your pocket, take it out to cool down a bit for the best difference. Also if your wifi was off, turn it on and give it a few minutes to warm up that spot) When I turn wifi off, the screen is uniformly cool to the touch. This is a poor-man's experimental proof that 2.3.6 messes up wifi in galaxy s2. It is overheating for some reason.
2) I also noticed that now there is a service called NFC that I occasionally see running. I don't think I saw it in 2.3.4. This probably activates the near-field communications card which I think is present in s2 but was not active until this update (?). Can it be interfering with wifi and causing extra battery drain? (doubt about this one, but still maybe someone knows)
3) Would like to resolve battery drain problem ASAP. Anyone knows how to roll back to 2.3.4? I want my 2.3.4 back!