I think the general consensus on here is that if a runner has not a clue about the route and has to rely 100% on the little arrow on the screen he is not going to be competitive as he will have to slow down so much becasue he is not able to watch the ground. He will probably spend half the day tripping over rocks and back-tracking becasue the resolution of the screen is not good enough to identify precisly where to turn.

How can somebody like that destroy your day so much that you have a wasted journey?