Hi, Two days ago I updated to IOS4 and the battery drained too fast!!!! In the night while it is in stand by mode the battery drops from 80% to 15% doing nothing for 6 hours..... I turn off notifications.... and the problem persist... Today I turned on "Airplane Mode" when the battery was at 15%...... this switch off wifi...but you can turn on it again in this mode.... and two hours later .... it was at 15%.... no drop!!! and the wifi works like before, i received my email while it was in stand by....as did before with IOS 3... I recharged to 100% and now 4 hours later the battery is 95%.. that saves alot of battery!!! Why they put "airplane mode", isn't more correct "Persistent Wifi" ON/OFF... O "Save Mode"? I whish it works to you too!!!