Rather good as a navigation tool.
I have, for some time, used an android app for navigation on my bike. It is pretty essential and HERE seems to be about as good as you can get. I can here the Google maps lovers ready to hit back and my life would be so much simpler if I could use Google (a mapping service I contribute to) but off line maps is a must for me.
Having said that HERE is slow to update and act on input but until the day whole maps can be downloaded for Google for off line use it will remain a back up service when mobile.