Rod1. Your para 5; agree entirely.
Not GPS but the number of times I've flown abeam the LIC NDB and watched GA traffic pass its overhead at similar levels but seemingly oblivious to each other's presence is quite alarming.
For the record, I do not want any transponder in my aeroplane (I've better things to route the limited juice through and squander lift on); ENDEX. I have windows and perfectly good (and trained, disciplined) MK 1 eyeballs.