I find if I follow a course the map screen becomes a blue line, I guess in a grid based system this is acceptable, But where the roads are irregular, it is very difficult. The Edge 520 worked better than that and with the same Open street maps.
Just back from a weekend in Holland, And with a 5 ways on the road and a cycle path round the outside the blue line was little help. Further from Hoek van Holland to Den Haag the blue line was ok west -east and slightly north but for the reverse journey the blue line had to be mental reversed, not easy at speed.
Why is it that it is advertised with Maps but as soon as you follow a course, You can not use the advertised maps. The way I see it is with all the side roads as thin black lines you have visual clues that you are two turns before your next action or this has 5 turns I need the third. etc.