I have both and they are both 2-3 years old. I cannot speak to the current design.
My house seems to have serious interference problems. None of the thermometers works beyond about 20-25'. The Nu-temps are what I use because of the PITA reconnecting the ET-73 when it looses connection.
Since I am not where the thermometers are, the following is from memory: With respect to the switch being behind the ET-73's door, this is to put the switch behind the weatherproof barrier. Be sure that you put the gasket back into its proper position when closing the battery door. The suggestion to drill a hole for a toothpick would breach this barrier and allow weather to get into the electronics.
Since I managed to toast two of the three Nu-Temp transmitters (yep, they were sitting on the Genesis shelf, too close to the fire box, while I was burning off the WSM grates; amazing what lots of heat does to thermoplastic and LCD displays) I probably will buy more of them.