Our system, iMac, printer, scanner, are feb via a surge protector. When the Mac has shut down I just switch the power off at the surge jobbie. That way everything is isolated in the case of storms and 2 switches switch everything on again. The printer is never physically switched on or off at the printer.
Ours is an HP Photosmart and if it is doing any of its houskeeping I just wait till it's finished to switch off.. Mind you, it almost threw all its toys out when I was fitting the CISS ink system and while powered on, opened the lid and pulled the plug. It complained when I plugged it in again. It had to be powered off while I was fitting the new 'cartdidges' and ink tubing. No more ripp off cartridges from now on 8) 8)