flyingwysiwyg
A moving-map GPS needs virtually no user interaction.
You just switch it on and when the signal is received, the map shows up. The only head-down thing one might be doing is entering / editing a flight plan and that one should definitely do on the ground.
I don't know why one might spend 20 mins fiddling with a GPS when airborne. It tells you directly where you are, where you are going, and what nearby places are called so you can reference them to the chart (and visually identify them) as you go along.