Nokia Drive (i.e. the navigation software) is a great app, as usability goes. However, I agree with @JohnAskew about Bing Maps. The turn-by-turn instructions (although requiring manual invocation) have been pretty rock-solid in terms of accuracy. Nokia Drive once had me driving around in circles while looking for the Santa Clara Microsoft Store, of all places.
Until the turn-by-turn data gets updated and the software gets integrated into the local services, Nokia Maps/Drive can't replace Bing Maps.