Outlets hammer height
switches 42" to the bottom of the box, easier to measure to bottom, and sheetrockers only have to cut one board, so you don't get loads of joint compound smeared into the box.
Kitchens 46" to the bottom of the box, has worked out in every house I've done. Usually puts the outlet midway between counter and top cabinet.
On stairways and landings I try to compensate for the depth or height of the landing to make the switch comfortable for the owner. I try not to deviate from the stock heights, because it makes finding a buried box harder, when you have to guess where to look.
