On the USB-connected systems, I get a lot of 'vetoed power requests' and such and it is not uncommon to get the 'lost communication' messages either. The USB is just tricky. Go with serial if you can ...
Power in my house is awkward. Unreliable for starters, hence the UPS, but also sparse. So I have 1 socket into which I have plugged 1 UPS, but I'd like to use it to power down 2 devices: 1 being my PC ...