I wonder if there were any issues with the STBY button being located where it is. It seems really risky place to have a off key right between other frequently used button.
Nah, they put a couple of precautions in to make sure you couldn't put the computer into standby accidentally. First, software has to set a bit to enable standby mode to be entered. For the astronauts, this was keying in VERB 37 ENTER 06 ENTER, which started P06, the pre-standby program. They then had to press and hold the button for a period of time between 1.28 and 2.56 seconds (exactly how long it takes depends on where the clock divider chain was at when they first press in the button). To bring it out of standby, you have to push the button in for a similar duration.