have to agree with IBLB in saying you should learn to navigate without GPS. Very important. However because GPS is now so widely used i think it should be part of a PPL course to be able to put in a route to a GPS, understand what all the different things are i.e. dtk, obs etc. (they are mostly industry standard) and understand how it will go wrong and that it can go wrong. Not that a VOR or NDB wouldn't go wrong.
A perfect example of this would be my Dad. He bought a brand new Cessna 182 about 5 years ago after getting his ppl. It was FAA IFR equipped but that was irrelevant because he had no IR. He had no idea how to use the equipment in the aircraft only the VOR. It was easy for me to pick it up but he grew up without all this stuff so he found it a very slow process. I think that if his PPL course had outlined the GPS use then it would have made it easier for him.