So, I heard, every now and then it seems to have trouble switching power states say from being connected to a power source to using battery.
It, as I heard, causes the device to not respond at all to screen touch input. So the phone cannot be unlocked. One difference in iOS7, I heard, is that the home button does not unlock the device. One can ONLY swipe to unlock it.
So, I heard, it will respond to a long press of the power button and show a "swipe to power off" band. But then of course the screen does not respond to touch.
The only available option is to soft reset it (holding both power and home button until it shuts off). After which, I heard, it still will not respond.
It only responds when connected back to power for a few seconds, as I heard.