I've handled various cars with inbuilt GPS, ranging from passable to appalling.
Indeed! But my trusty Garmin nüvi 600 always travels with me and has never let me down.
A German colleague and I once hired a car at Hamburg airport. As soon as he fired it up, the SatNav pointed directly to Poland, so I asked in mock innocence whether there was any particular reason for that - was it historical? After fiddling for a couple of minutes, he entered our destination hotel and off we went. He knew a better route once we were over the Elbe, but the SatNav wanted us to go a different way... A few "Bitte biegen Sie nach 500 Metern rechts ab" and the like in a polite female voice, with increasing urgency as we got closer to her preferred turning, until 'she' suddenly shrieked "JETZT RECHTS!" like some whip-wielding Brunhilde from a sex dungeon*. As we went past, there was a pause before she sulkingly announced "Neu berechnen" in such an annoyed tone that had us laughing aloud.
* or so I understand - but not from personal experience!