I have been using the Bing Maps navigation functionality in Windows Phone Mango on my devices and it is decent. However, the fact that you have to tap to hear each turn is lame. I look forward to seeing what Nokia brings to the table with their navigation solution, but at this time that is a big unknown on Windows Phone. One new application we do know will provide an excellent navigation experience, with offline mapping support, is NAVIGON for WP7 that is coming soon.
I've used NAVIGON in the past and thoroughly enjoyed it on iPhone and Android devices. WPCentral has a few details on this new version that runs on Mango and takes advantage of the new Mango features. The following statement appears in their press release:
NAVIGON’s premium navigation app soon will be available for Windows Phone 7 users. The app includes many signature features that have made NAVIGON’s apps successful on Android devices and the iPhone, including on-board maps, spoken turn-by-turn directions, visual lane guidance, live traffic information and rerouting, among many other features. NAVIGON’s new app runs on Windows Phone 7.5 and also takes advantage of new features made available to developers with this new release. These features include the augmented reality function Reality Scanner, which provides an instant and effortless way of identifying nearby destinations while on foot; an option to select address information directly from the phone’s contact list; and the ability to save a favorite or home address as a shortcut on the start screen.
I like that they are offering full support for a walking mode with their Reality Scanner too since I often use GPS navigation solutions when traveling in new cities and often that is on foot. Their lane assistant is also one of my favorite features since there are some confusing highways out there. I plan to get this on my Windows Phone Mango device as soon as it is released.
They also announced updates to their Android and iPhone apps that include new map management from a web browser, redesigned user interface, and much more so if you have the app on those platforms go check for the free update.