Twice I have used google maps to try to find somewhere in Sydney and twice it failed. I find that the maps can't update fast enough and the position updates in jerks of about 100m so I found I went past my turning but it showed I had not yet got to it. I also find it very innacurate especially when going round corners. It usually has me going through buildings or trees.
I have some of those map my trail type apps which plot your route on a map and that is running or walking. I had a look at some of the demo trails plotted on a google map and even in the US I saw that some guy had walked on water at some stage so it again was inaccurate.
See this map-if you zoom up you can see on a few occasions he walks on the river
http://pathtracks.com/users/1/paths/1 or even worse
http://pathtracks.com/users/1/paths/4-freeway-driving-ipod-touch where he drives through entire blocks of buildings in Denver. In fact he drives more through buildings than he does on a road, seriously, take a look.
I would love it if google maps was good at real time navigation but my honest experience is that it is worse than a paper map.
Sorry buy this is hopeless for real time navigation and these is my experience in Sydney.
Hopefully some real gps apps will now come out to compete with x road.
I honestly have no axe to grind in making X road a success but I need something better than Google maps and I will get a Tom Tom unit if they don't release a decent iphone navigation app for Australia