Ok, this is written after a few pints of Black Dragon cider so bear with me, it might make sense but I'm not promising anything.
GPS Navigation is great as long as you realise the limitations of the system and use it in conjuction with a map and compass. DON'T RELY ON GPS ALONE! Your Gold Standard for navigation is your map and compass.
As an ex mountain rescue member our navigation skills were constantly practised and honed, we sometimes used gps to get precise fixes on location but these were always backed up with observation of what was around us. if the GPs says your 150m away from the bottom of a cliff face and you'r stood at the top of cliff face, then something is not right and other methods of fixing position is needed. This is where the map skills came in.
Map reading skills are probably one of the most important skills you can learn to go out into the mountains. when the weather closes in, your GPS stops working, you're cold, wet, miserable cos youve finished your last mars bar, you use your map to get yourself out of trouble.
We had, just before I left the MR, started using GPS radios which reported your position on a laptop at base as you used the radio to relay info. the tracks from this info was very interesting to see, sometimes the track was way out, sometimes it was spot on
As to expecting to be rescued when things go wrong, remember that ALL Mountain Rescue services are volunteers, they don't get paid, a lot of their kit has been paid for by the members themselves, each MR team is a registered charity. THEY ARE NOT OBLIGED TO TURN UP TO RESCUE YOU. More often than not they WILL turn up to rescue you, and sometimes put themselves at considerable risk doing so, and sometimes put themselves out of pocket in lost earnings, damaged equipment and so forth. A lot of people think that the RAF and their big yellow helicopters are there solely to rescue people when the fall off mountains, this is not so. The RAF Rescue service is solely for the rescuing of downed pilots. The fact that they go and rescue mountaineers and hikers is purely out of goodwill on their part, again, they are not obliged to turn out to rescue you when you fall over.
So, IMHO GPs is ok, but make sure you know how to read a map and use a compass. And at least have a orange plastic bivvy bag and survival blanket with you in case things go wrong, and a whistle too!
Another pint methinks, sorry about the rant.......