MJ
I was merely pointing out that someone saying (paraphrasing) that Joe Smith, 75, was sitting on his boat sometime last year and 6 months later reported, over not a few pints of Guinness at the Rose and Crown, that his trusty old GPS wasn't working for half an hour, doesn't amount to good evidence of GPS unreliability. Yet this is the sort of "evidence" we get all the time.
A few high-hour pilots on Prune saying they've never seen problems doesn't amount to categorical proof of GPS reliability, but it's a whole lot better supported than the above. From my own point of view, I know a good number of IFR pilots with modern "IFR GPS" gear (which, in the UK basically means KLN89/90/94, GNS430/530) and none of them has ever had the slightest problem.
There are reports quoting frequent losses of accuracy, say from 20m to 200m, and make a meal of that. But for en-route navigation, 200m is NOTHING, zero, zilch, utterly irrelevant. And one cannot use GPS for anything else other than en-route (yet). GPS accuracy could be degraded an order of magnitude and nobody in GA would be affected - although it would show you on the wrong taxiway
The U.S. economy is heavily dependent on GPS now. They won't let it fall apart. Who says the system is reaching it's sell by date? It works perfectly well.
The Europeans will have Galileo to give them theoretical independence from the Americans (always a good topic on which to get the Brussels crowd working on yet another device to immortalise themselves) but they will charge for the high accuracy signal. Not that that matters, because the GPS, even with its worst errors due to selective availability, was miles more accurate en-route than anything else. But your airliner IRS will sync from DME/DME anyway, whenever it can.
I sincerely hope that fibre optic gyro IRS will reach GA long before 50yrs from today! The JDAM package reportedly goes for about US$20k and that has a FOG IRS, a jam-resistant military GPS, servos, you name it.
EVO
Yes, I think training is the #1 problem. But the powers to be, as well as much of the old crowd, have dug themselves so deep that bringing it in formally is just about impossible.
Putting a GNS430 or similar in a plane flown by a new PPL just makes matters a lot worse... but that's what happens when technology moves along but the regulatory powers pretend it doesn't.
The best single thing the CAA could do now is mandate a rooftop GPS aerial. But then they would be admitting that GPS is OK to use in some circumstances, and they can't possibly do that... and lots of people would be sure to moan about the £500 cost. And they can't be seen to regulate portable equipment so they would have to mandate a panel mounted unit, and who will pay for that? It's Mode-S cost, roughly.