I have yet to have my iPan Mini (original version with cellphone & GPS) fail--no overheating, no glitching in the air. I have had it glitch a couple of times on the ground, but I had gotten into the habit of adding this or that app that struck my fancy. So I pulled off most of the non-nav stuff, and the glitches have gone away entirely. What's left is enough to do a little web surfing and emailing, and Foreflight. I use it for my charts and approach plates, and I have FF in my iPhone 5s as a backup, although I've yet to have to resort to it.
But at this stage of "NextGen", I would not recommend to anyone that GPS be the sole source of electronic navigation. The DoD is still regularly doing its testing, and that means that during the testing, the GPS can go off line at worst or provide inaccurate information at best. The map functions of FF and the iPad will still work, just not the GPS driven functions.
So although I like my 430W and use it a lot, I'm not about to give up my navcom or my ADF. Even in solid IMC, I could still easily get close to my destination without the GPS side of the 430W, shoot an ILS or VOR approach, or even an NDB approach if still available.
And if the clouds aren't in the way, I can still use pilotage and ded reckoning to get there. Not sure I want to learn how to use a sextant, but I'm still pretty good with a stopwatch, compass, and chart.
Cary