I know that's what you good navigators do ShyTorque its what the not so good navigators do that worries me. There's ample evidence in the preceding posts that there are quite a few poor navigators flying around the skies, some of them 'Professional Pilots' too!
As a long time and highly qualified avionics specialist I've yet to encounter any foolproof 100% reliable navigation system. No matter how good and reliable the GPS is, the airborne equipment carried in today's aircraft is the same old junk that we've always had in aircraft. If avionics systems were indeed perfectly reliable, I wouldn't have a job.
As a member of the Royal Institute of Navigation and avid reader of the Institute's Academic Journal I'm also well aware of the considerable shortcomings of GPS. It isn't anywhere near as accurate or reliable as so many people seem to think - which is why the Institute recommends caution when relying on it for primary navigation.