Crapnav is a disaster - I used it once and was so shocked at my resulting complete ignorance of my whereabouts that I have never touched one since.
I agree that for a truck or delivery driver or taxi in an unfamiliar area it has its uses but leisure users are much better off with a map, which gives you much more information. Using a crapnav is the equivalent of using a map but viewing it through a long thin cardboard tube.
I was driving to meet two colleagues at a restaurant recently when I spotted a go-slow on the motorway so I dived off and joined the old parallel A road. Called my colleague who was following a few minutes behind and told him to do the same. So what did the feckin' eejit do? He left the motorway and when the A road reached the next junction he blindly followed the crapnav's instruction to join the motorway..... straight into a monster go-slow!
The only time I use the satnav I carry with me is when I decide that I'm totally and irrevocably lost!
The last time it happened, when I finally chickened out and fired up the satnav I found that I'd spent over an hour, struggling uphill across muddy fields to end up within about 50 yards of where I started from!! I don't often get lost but when I do it's usually a howler