A few years ago when I was flying GA, there were loads of threads on here about the fact that GPS navigation could never catch on and should never be relied on.
Can you believe we used to go flying with a whizz-wheel clutched in our clammy hands together with a chart measuring 1m x 1m. on which we had made marks with china-graph pencils. The Pooley's book with the airfield data was also kept somewhere handy. We actually used all this stuff for primary navigation.
"dont ever use a GPS unit while flying, they are bound to fail and then what will you do?"