I don't understand why all mobile makers are so touchy about turn-by-turn navigation.
When you've paid for the map data, and got GPS hardware in your device, it seems crazy not to implement turn by turn navigation, since the added software development cost is pretty minimal.
I suspect the problem is more of a licensing one - for example, when turn by turn navigation came out for android, it was US only for a while. A hack existed to enable it in the rest of the world, but that was soon stopped by google. Only later did it get released for the rest of the world.
Considering that it worked with a hack, it can't have been a softwatre issue that was preventing worldwide release - the only possibility is that licensing and company politics was getting in the way. Maybe people like tomtom get exclusive rights to do navigation on map data, and therefore while google has rights to use the maps, they don't have rights to do turn by turn directions with them?