Re: My experience
"Myself, I have a really good TomTom Premium X I can put in any car, and it's golden. I can even navigate a map on my computer, and push it to the device !"
Same here, although a decent Garmin in my case. In-car sat-navs were pretty shit in the various hire cars I've had over the years. Usually out of date, hard to use, too low down to see properly without taking your eyes off the road, and often poor at routing or re-routing.
Cheap SatNavs aren't a lot better and Googles Maps is barely useable for car navigation because, as you say, too much unwanted shit on the screen.
It helps if, when buying a sat nav, the buyer looks into it properly as with any other tech purchase and looks for something with support and updates, especially mapping updates.