The following is directly from the FAA web site as of today. Reading this it would appear it is up to the discretion of the carrier/pilot.
This does not make sense to me because if a PED effects the electronics in a Boeing 737-300 it should not matter if the 737-300 is flying for American, Delta or United.
http://www2.faa.gov/avr/afs/cabinsafety/FAR's/91-21.rtf
Through the fish-eye lens of tear stained eyes, I can barely define this moment in time...That is until I bought a GPSR.