From the Windows Phone blog:
The app remains in beta as the team fine tunes the customer experience. In the meantime, you can access full turn-by-turn voice-guided navigation, offline maps, speed limit warnings, and conveniences such as day and night modes. With today’s release, the team is looking forward to hearing from even more Windows Phone customers through the app’s “feedback” tab, to help make it even better. Give it a try and let them know what you think. Learn more about Nokia Drive+ Beta .
Having been reviewing the ATIV S and HTC 8X recently, it was painfully obvious how each of them was (to some degree) hampered by not having a proper navigation solution onboard (when compared to Android, iOS and Symbian) - with today's release, we're seeing the 'rest' of the Windows Phone 8 world now brought up to par in this area and this will make the HTC, Samsung, LG and ZTE (etc.) devices potentially more attractive in the long run.
It does remain to be seen, of course, which of these manufacturers actually bundles Nokia Drive+ in their firmware (as opposed to letting users search for it in the Store).
Nokia Drive started life on Nokia's Symbian platform, of course, though functionality on Windows Phone is now approaching parity with its older implementation. It's somewhat odd to still see the 'beta' label applied to it after a year of availability, but then Gmail was in beta for many years, so....(!)
Regardless, this is a major addition to the Windows Phone 8 'platform' and will be welcomed by all. Now we wait for inclusion in firmwares and for a true worldwide rollout....