The problem with google nav is that the times you most need your satnav to work is when youre lost in the arse end of nowhere. i.e. the sort of place where there is no data connection.
The very reason i bought copilot was because i decided to check google maps on my phone to help find out where i was. The GPS in the phone pinpointed my location precisely and displayed my exact location - in the middle of a blank screen. Highly accurate and completely useless at the same time. Had to resort to a paper road atlas at that point.
Copilot isnt perfect, the UI is a bit clunky, but it works. Unfortunately it hasnt solved world peace or made my life complete but what can you expect for $35? Shrug.