What's the best navigation app for the iphone 3Gs and later? I know that the iphone 4g and OS 4.0 are both being unveiled on the 7th; I'm planning on upgrading to the new phone when available. Unfortunately, I don't have any expectation that Apple will include a comprehensive turn-by-turn navigation app with the new phone hardware and OS. Assuming Apple doesn't come through with the amazing Google Navigation currently available gratis on Android phones, which navigation app is currently the cream of the iphone crop? Thanks in advance.