I disagree with this. I have a Nuvi 550 GPS, there is no way that I want my iPhone tied up with navigation duties for long stretches of time. While the iPhone

I disagree with this. I have a Nuvi 550 GPS, there is no way that I want my iPhone tied up with navigation duties for long stretches of time. While the iPhone can theoretically function as a GPS, or a Kindle, I don't think it particularly excels at either function as is no real threat to those devices.