It definitely had an effect, but not on my external monitor. I have that plugged into the monitor port on the back. When I hit the keys you recommended it cut my existing screen in two and swapped their locations, but had no impact on the external (and I did make sure it was connected and powered on).
I unplugged it and plugged it back in, and checked the var/log/messages; it's not adding a message when I do that. I wonder if that serial port is even on... but don't know how to check.