Power Button unresponsive. Used "accessibility" settings to turn off iPhone. Plugged into charger to turn on. A pain in the you know what.
The power button was fine. Per ifixit, I went directly to replacing the iPhone 4 Power and Sensor Cable. Viola!
(1). Tape the screws down on sheet of paper and label the step involved. (2) When different sizes on a single step, label screws "orange" "yellow" per the direction diagram. (3) Buy a desk lamp with magnifier. CRITICAL to see the small connectors that need to snap back together (4) Take your time!
Phillips #000 Screwdriver
P2 Pentalobe Screwdriver iPhone
iFixit Opening Tool
iPhone 4 (CDMA/Verizon) Power and Sensor Cable