OP...
Have a 3GS and exactly the same problem, so does my wife. Since the 4.3 update battery life is appalling. I have quit everything and it is still losing between 30-40% overnight, around 8hrs.

In my view it's not the battery, and 4.3.1 has been installed on my handset since Friday and..... No difference.

I charge mine overnight but am now finding that I need another charge in the afternoon.

I'd turn off push notifications and use polling let's say every hour instead. Do you have some overview what app uses what? There's something like that on Android phones, not sure about iOS. Nowadays every app wants to check something over the network Also is it possible to turn off multitasking? I know it's not turned on on 3G models. Usually you don't really need it and all the background processing just drains the battery. I would also look through the settings and check if they changed/added something that needs turning off.

IvanIV,

Have 2 3GS handsets, one running iOS 4.2 the other 4.3.

Both have the same apps running in addition to the standard apple offering pre installed. The 4.2 version loses around 4-6% overnight compared to the 4.3 version as stated in my earlier post.

Now, I do nothing different, signal strength is excellent in my house but when we checked them over the last few nights the remaining life was noticeable.

Apple reckon they have identified a possible problem (see apple support forums) but its not conclusive and knowing Apple they wont let on but will rather sneak an update out with something disguised in the small print but that could be anytime. Seeing as 4.3.1 has just released i reckon a couple of weeks minimum.

As for in the meantime, nothing, cant do a lot other than continually charge the 4.3 version.