This is kinda driving me nuts. When I press the power button to lock the screen there is now a few seconds delay before the backlight cuts off. So I end up staring at the phone when it should have already been in my pocket. I know it's related to ICS, but it hasn't been consistent. Sometimes it cuts off as soon as I press the button; most of the time, not. The screen is locked before the light goes out, but why would you not want to know instantly that the command registered? Obviously I'm done looking at the phone once I press the button.