The People vs GPS

What is the real purpose of GPS?

I ask because I only have a couple of friends who had GPS devices and they seem to have a complex relationship with them. I have always thought that if I had a GPS it would serve my purposes as follows: I am driving. The GPS gives me directions. The end.

It doesn't quite seem to work out this way. A friend of mine with GPS built into her car seems to be in constant dispute about the GPS's advice. So every time I go anywhere with her we end up in the following situation:

GPS: In four hundred metres, turn left.
My friend: Oh god, it wants me to go round the M25 again. No. I am not going around the M25. I'm going to take the North Circular.
GPS: Turn left.
Friend turns right.
GPS: Do a U-turn.
Friends: No! No, I am not doing a U-turn. I am taking the North Circular.
GPS: Do a U-turn.
Friend: No! Shut up!
GPS: Do a U turn.
Friend: Why does it always want me to take the M25?
GPS sullenly displays a big cross.
GPS (suddenly, unexpectedly): In eight hundred metres, take the second exit from the roundabout.
Friend: Finally! Finally it figures out what I want to do! At last!
GPS: In three hundred metres, turn left.
Friend: No! No, I don't want that exit! I'm going to ignore it.
GPS: Do a U-turn.

And so on. In other words, when my friend's husband is not in the car, the GPS exists not to give my friend directions, but to provide her with someone to argue about directions with.

On the way back from our booze cruise to France this weekend, another friend decided to switch his GPS off for half an hour to help preserve the batteries. After a while, though, we decided we weren't entirely sure where we were going so we switched the GPS back on.

GPS: At the next roundabout, take the fourth exit.
Friend: Oh, that's making us go back on ourselves. We must have missed our exit. Thank goodness we switched the GPS back on.
[Forty five minutes later....]
GPS: At the next roundabout, take the fourth exit.
Friend: Uh - hang on - that's making us go back on ourselves *again*.

Yes, out of revenge for us having switched it off, the GPS made us drive the same stretch of the M20 three times. In this case, the GPS appears to have taken the persona of a petty, vindictive boss.

Do all GPS's have their own unique personalities? Or is there a limited set that you can choose from when you turn them on? Do other people's GPS's sit on the dashboard muttering "OK, Mr Clever Clogs, you turn left if you want to" and then, one lost hour later, "I told you so"? Or maybe, when you have just turned right under its instruction, say "Oops, I meant *left*, silly me, I always get those two mixed up"? Can you get a GPS that spends the entire journey singing to itself and then, when you have accidentally ended up in Aberdeen, says "Oh I'm sorry, was I supposed to be looking where we were going"? (Or is that a radio?)

I think I'll go for a GPS personality that knows exactly where everything is, doesn't make dodgy direction decisions for me, doesn't talk to me in an irritating schoolmarmish voice, and never runs out of batteries at the exact critical moment that I am getting lost. Or to put it another way, a map.