Sat Nav App for WP7

I recently went looking for a good sat nav software for my Windows Phone. Even with mango, Bing Maps is nothing more than "all right".

Sure it can get me from A to B. But doing so in an easy, safe and convenient manner whilst driving seemed to cause it issues. I mean really, it doesn't update the instructions as you pass them, so the onscreen information is still showing you how to get out your street when you've hit roadworks half way through your journey and need a plan B. And don't even get me started on a lack of turn by turn voice directions.

So I went looking. And sadly found no good free apps. However, I did find a rather spiffingly good app that comes at a cost.