I've never heard them mention GPS. I use mine on flights. I enjoy connecting it to a laptop with Street Atlas USA -- then I can look out the window and identify things on the ground. I know, it is not terribly exciting, but it sure beats reading the in-flight magazine again!

I was questioned once about the GPS and the FA said that she would ask the captain -- he said "no problem".

There is some information about this on the CO website at Electronic Devices

"Devices that are not permitted for use at any time:"
[...]
"radio receivers and/or transmitters (including AM/FM/SW, CB and scanners)"
[...]

I'm not a technical expert on GPS receivers vs regular IF-based radio receivers, but perhaps somebody with real-world technical knowledge could enlighten us with the differences?

Here is a government report about electronic device hazards on aircraft.

It mentions GPS as permissable above 10,000 feet: [...] "In the middle of these two extremes are portable electronic devices that can only be operated before departure, while the aircraft door is open, or after the aircraft has reached an altitude of 10,000 feet. When the aircraft is descending, all PEDs in this category must be turned off. These actions are usually controlled by flight attendant announcements throughout the flight. The PEDs subject to these restrictions include CD players, laptop computers, electronic video games, and GPS navigation sets. "

When it doubt, ask the captain! -- it is their flight and if there are safety concerns, they can make the decision.