Last year bought 3rd gen ipad uk 3G and wifi. Sky demon on ipad.
Flew VFR to Mallorca.
Was not sure about all the GPS issues you raised but. ....
Didn't lose signal once.
Best touring device I have ever had
Once a day on ground wifi and notams and weather all downloaded, more often when wifi available.
My view as humble vfr tourer is that this is the most useful device I have come across.
Notams, weather plogs airfield plates all on ipad.
Faultless gps navigation.
Little else to say. Best tour yet.