A GPS without a moving map is OK for a door stop, nothing else.
Only is someone is a fcukwit and doesn't know how to use it
I usually on a long cross country backup the 496 route onto my trusty eTrek - i download the route from my PC to the eTrek. Then if the 496 packs up I have some navigation. I also have a load of waypoints in my eTrek that I can use and worse case, I can manually enter a point.
The mean time between failures for conventional instrumentation is in the region of 800 hrs (FAA stats). For the Glass panels - and I suppose it goes for the GPS units like the 430/530's it is over 2000 hrs...