One of the great features of the new iPhone 3G is GPS. It did not take long to find out. You can use this feature with the Map app. Simply identify where you are going to enter the address, then choose Get Directions to draw the shortest distance. When you are ready, select "Start" and the 3G network will search for a pulsating blue dot on the map. As you move, this will be the point. Definitely good.
I noticed some fixes that would make it better. One would be a voice command that asks the user to turn or when a turn comes. The other one would be if the map would turn out to be always on the screen. You have to change the iPhone at this time after you have made a change of direction if you want to move in the same direction as the blue dot.
Instinct's commercial report has a GPS voice command. At this point I would say that this is the biggest competitive advantage of the iPhone 3G. Instinct's GPS would respond far less than the iPhone. I noticed that sometimes I've been through such streets that the iPhone GPS did not show. I would say that the service is definitely useful if you plan on a long journey, I certainly do not trust you to get to me without some mistake.