I simply couldn't find a way to display Directions with the international SI unit km (kilo-meters) but only in the weird Miles.
1) autodetect the country of the browser or where the Bing Maps are displaying and use the locally used distance
2) or use the home of the user
3) or add a way to change the miles <-> km (maybe clicking on the unit?)
4) colour clickable texts differently than normal text, it's really difficult to "know" what can be clicked. (This is general for Windows Phone and Windows 8)