I like the idea of 'alternate routes' as I often do this manually by adding 'waypoints' if I don't quite like the one calculated. I always use the fastest option so that road preferences and speeds are taken into account.
How does Navigator ensure that it follows the route option that you have selected? Does it add waypoints? What if If I want to use a town ring road when it suggests driving straight through can I add a waypoint or will that defeat the chosen alternative?