We got a new car recently, and I was playing with the nav system and having it navigate while in somewhat remote places where I already knew the way. It was disappointing how often is wanted us to do some nonsensical loop. Although, that isn't as bad as when my friends iPhone GPS told us we were at our destination after instructing us onto the freeway overpass that was above the address we gave it.
I download topo maps to my GPS, as matching up terrain features is a real clean way to confirm a location on a paper map. Although, I've learned to use my GPS very sparingly, only turning it on when I'm not 100% sure about something... or to get my companion to stop arguing with me about what direction we should be going. Early after getting my first GPS with topo maps, I found that by actively looking at it while hiking (especially bushwhacking) it becomes strangely disorienting and I'd end up veering off course frequently. I get a kind of tunnel vision and I stop really paying attention to my surroundings, but rather focus in on which way my little icon is pointing. I've never felt more lost, then while trying to look at my GPS while moving.