If the applicant says that he knows how to use the installed GPS, I let him use it during the diversion on the second leg of the PPL Skill Test. Also the VOR/DME and ADF. But only after first working out track/dist and hdg/eta by conventional MDR.
After 5-10 min flying the diversion planned by 'conventional' MDR techniques, the confidence the student gets in seeing that his MDR agrees with the GPS is well worth the effort!
No reason not to move with the times, but I do think that there is some need for the student to understand the basic principles. Navigation is the worst taught part of PPL training; most new FIs confuse the student with pointlessly excessive RT work and encourage too much map reading.
In any case, navigation can't be difficult if navigators can do it!