I just discovered a free GPS app for my iPhone called Waze. Free is usually an indicator of a light version of a full app. Not here. I have played around with and paid for some full featured navigation apps and have not been terribly impressed. I actually just drove from NYC with my brother, to Greensboro NC. We had two iPad, two iPhones and a built in GPS in my brothers vehicle. It was a Mo, Larry, Curly moment. We stopped multiple times by the side of the road to determine why all the devices were giving us different info, and actually got lost once. I am just glad my wife wasn't in the car or I would still be hearing about it. Anyway, I digress.
I downloaded Waze a week ago and have been testing it out. It is not only a reliable GPS navigator, but it learns my most favored routes as I drive them. For instance I had it chart a route from my office to my home, but took a bit of a different way. The next time I asked it to show me the way home it remembered the route I preferred. Nice!
There is also a social aspect to the app as well. I shows traffic, speed traps, construction, and road conditions, as reported by other users. There is a dropdown menu that allows you to add any of these while enroute and as they are added, they load live for others to see. So, when you look at the map of your route, you can determine an alternate if there is traffic or construction or even know where there is a police officer waiting to help make a withdrawl from your checking account.
Personally, I don't know if this app would have kept us from getting lost on the way to N.C. but I am wholly impressed with it so far. You can watch a demo of the app here.