We already know that Nokia Maps won't be making it directly in Windows Phone devices with Mango, but will rather appear at a later time, when the daunting task of converging Bing and Nokia maps over the underlying Navteq cartography is finished. So free turn-by-turn navigation will be on WP handsets courtesy of Bing Maps only for now, that is why it's interesting to see how it behaves.
For now Bing doesn't cover nearly as many countries as Nokia Maps with detailed routes, not to mention offline availability and voice guidance, but, until the update hits, that might be changing. Still, for now Symbian will remain the king of free offline navigation, courtesy of Nokia's Navteq purchase a few years ago. Have a look at what navigating with a Windows Phone will feel like on a Mango-ified handset.