This fixed it for me...

I rested my iPhone 4 onto my 4S and was ready to demand a refund when the battery would fully discharge whilst I slept every night (and I don't sleep that long!).

I was serious upset and not happy to turn everything off to try and make it work, as what would be the point of upgrading.

Anyway, I tried lots of the solutions and as with a previous upgrade (may have been the 3 to the 3S) a lot of the problems seem to come from restoring settings made for the previous model onto the new one.

I found that if I did a 'reset all settings' (you don't lose any data/contacts/media) that after a further power cycle of my phone I'm suddenly getting good battery life (well similar to my iPhone 4) without turning off all the nice new features.

I can now easily go a full day again with my normal usage without worrying and lose about 1% an hour overnight (the phone checks email every 15 minutes), which I'm happy with.