when you are on picture taking mode, press "disp" and it will turn off..
it looks like the cam is off , but the lens is still out
yea, i didnt like how the battery sucked on my S100, good thing when i got the S110 its alot better.. i usually go thru an entire 128 MB CF before i need to recharge the battery...
i would just get another battery, use that newer one as your primary one and keep this one as the backup