The handheld GPS is a great toy and a wonderful gimmick, but no replacement for a chart. Often, that's unrecognized or forgotten, occasionally to the detriment and even loss of life of the forgetful.
Well, I am not sure I agree.
I have flown for way over a 1,000 hours using only a hand held GPS. In that time I had one GPS failure (my own fault) and another failure for other reasons. As luck would have it on the second occasion I also had some issues with the radio nav. equipment in poor conditions. I backed up my own nav. with a request to AT to provide me with vectors as I worked my way across Holland, France, and part of the UK; no big deal, but with some complicated airspace to negotiate and no wish to go IMC I was not going to risk infringing.
Hand held GPSs are almost certainly more reliable than most peoples ability to navigate any other way - at least over reasonable distance and terrain with which they are not familiar. Most of the time they are therefore better off following the magenta line and using the moving map to ensure they dont infringe.
The key is for them to have the sense to own up when and if the GPS fails. It may be embarassing but so what - a call to AT will readily sort things out. Those that are the real danger are the pilots that believe their "tradtional" nav skills are up to scratch - they dont know when they are lost, and they dont realise they have infringed. At least when a GPS fails you almost always know it has failed.
I enjoy a bit of traditional nav - it is my sort of thing. However my aircraft has twin IFR approved GPS receivers, glass screens and I still carry a Garmin in my flight bag. Why? Well all the time I dont want to worry where I am it takes care of the chore for me, provides unparalled situational awareness and enables me to transition to IMC should the need or the desire arise. Airways, why would I want to use anything else?
A GPS handheld or otherwise is not a toy - it is a serious piece of kit packed with technology. The chances are with a permanent power supply and an external aerial it will prove as reliable as a panel mounted unit, will have a failure rate way lower than your engine up front without any maintenance and, if you carry two, I doubt in a lifetime you would ever see a simultaneous double failure. In fact I have had more engine shut downs in twins that handheld GPS failures.
Fortunately I am ahead of the game in singles.