On Windows Phone, one thing that I like a lot is Nokia's HERE suite (maps and turn-by-turn navigation). Free and really good. The hardware is good and the OS is nice too.
One thing I was impressed is that it seems actually easier to develop for Windows Phone than for iOS or Android.
I have a Lumia 920 and I find the turn-by-turn navigation to be abysmal. It gives distances in yards and the vocabulary does not extend much past "keep right", "keep left", and "follow the course of the road". It's also flat our wrong more often than not where I live. Google tells you street names and exit numbers, which is vital in large metropolitan areas.
Also, map searching is no where near as good as Google Maps.
Two things: 1) you can change the distance units, and 2) the app will pronounces the names of many commonly-named streets, but it is certainly true that its vocabulary is much smaller than some other options.
