They're brilliant, and compared to a driver actually reading a map whilst driving (which I think safe to say we've all seen, and possibly even done) they're a godsend. My gripe, though, is that the TomTom I've used has the nasty habit of having absolutely no concept of distance - ie: you're told you're 50 yards from a turn, two seconds later you're told 'turn left' (!) this has the annoying result of one of two things
1. You miss the turn, as you can't realistically, safely turn in the given distance, then get it whining in your earhole for the next five mins as you make a 'round the block' manoeuvre.
2. You make the turn, hard lock with passengers thrown about the cabin, driving like an 18 year old the day after passing his test and being given a Scooby. Also means doing that oh-so-pleasant thing where you indicate
as you perform the turn, as opposed to mirror, signal, then manoeuvre, like what we're supposed to.
As I say, they're your choices. You have to reconcile/compare which you prefer - making the turn, and being moaned at by your other half 'why are you driving like that?' vs 'you missed the turn! Why did you miss the turn?'

I am assuming that the newer models have at least partially rectified this. Also as you say, getting confused which road you're on when you go over/under another road.
