I love satnavs.
For the past two weekends I've made the mistake of trying to drive around the country. On both fridays (17th and 24th) most of the country's motorway system ground to a halt, with the M6 closed, the M25 at a standstill, etc.
The prevalence of satnavs has made the majority of the populace, particularly when driving out of their local area, totally brain-dead when it comes to maps, alternative routes, etc when things go wrong. This means that when things do go wrong, alternate routes are left empty because most people sit there thinking "Well this is what the sat nav says".
Thus, while the M6 was at a standstill I drove merrily up and down the A449, and avoided the busy and roadworked M1 with a quick jaunt along the A38.
So, I love sat navs. They keep clueless people out of my way. I just don't see any particular need to own one for myself.