The problem is that ASUI always performs its action when the power button is touched, even for long presses, and for some reason MCE won't shutdown if the screen state is changing. If you secure lock the device and try long pressing it won't work unless you get lucky. Same thing happens all the time if you set the power button to lock&blank instead of mapping/unmapping ASUI. With raw power button events I can see down and up events and only trigger on the up event if it isn't a long press. It'll also allow ASUI to have another action bound to power button double taps.