Kurumi, you're not kidding. Couple years ago my brother and I drove his family and me in 2 cars from suburban Chicago to Virginia. (Keep in mind that he has a bigger lead foot than I but he was following me.) All was good until we got near Elkins WV. Somehow in the mountains along US 33, he got lost even though I told him that we are staying on 33 the whole way. When daylight broke at the VA/WV border, I pulled over to wait for him before getting into Harrisonburg. My neice and I waited almost 45 minutes before he finally showed up. Thank god for the Waffle House in Harrisonburg so I could calm down and not scream at him for being an idiot.
this must've been before cell phones. I'd done that a few times too... and we always made a backup plan of "find us at such and such a landmark in this town". If it was a town we'd never been to, it was the post office, as we figured it would be easy to find with local help. luckily it never came to that.
We used to do that on Boy Scout trips when I was growing up—on the annual ski trip to Seven Springs up in Pennsylvania, for example, all the drivers were to stop at the McDonald's in Breezewood to regroup before we got on the Turnpike so we'd know if anyone had gotten lost (and, indeed, one year someone somehow did get lost, though I still have no idea how). It worked pretty well most of the time.
I have a built-in GPS unit in one car and I quite like it for various reasons. While I tend to know where I'm going and what roads I want, I find that on a long trip on a road I don't use regularly it's nice to have the thing giving me distance and ETA. I like having the "find nearest gas station" or "find nearest ATM" or whatever, especially if I'm on a more rural highway in an area I don't know. Not all states are as good as others about posting signs for gas and the like. Also, mine has a joystick control option, which makes scrolling very easy—if I'm stuck in traffic and I want to find an alternate route and the sat-nav lady doesn't seem to want to give me one, I can shove the joystick around looking at options. The other thing about my built-in unit is that its voice control also controls the radio and the climate control, which can be very convenient.
A GPS unit can never replace a map for giving you the big picture and I think there's always a good use for maps at home. I also keep a 2005-era Rand McNally atlas on which I highlight the major roads I've driven or travelled in North America and I continue to update that (I just don't feel the need to buy an updated one). But when I'm driving I just prefer not to mess with a paper map, and my wife is not particularly good at reading them while we're in the car so I prefer having the sat-nav as a backup instead of asking her to look at a map!
My wife has a portable Garmin that is nice (I gave it to her after she got lost driving home from work once!), but I like the built-in device better.
Incidentally, going down a totally separate GPS-related avenue, I recently downloaded a pedometer app for my iPhone. It uses the GPS to track how far you've walked and it will draw a map to show you where you've been. I rather like that, not because I've needed it for directions but because it gives a good picture of where some of the local trails go and the like. We visited my parents on Sunday and I was telling them about a walking trail they ought to explore sometime and it was quite convenient just to pull out the pedometer app and show them the map it had made.