One thing that will be interesting to see is how at&t deals with the GPS issues. For example, on a blackberry the GPS works out of the box and is free (of course data is necessary to download map data). But, there are numerous applications that simply use GPS data to provide speed, directions, elevation, etc., and even to save tracks so that they can be viewed later on google earth and other apps.
However, at&t goes out of their way to disable the native blackberry maps application because they want to sell people subscriptions to telenav at an extra $9.99/month. Google maps is free, and I expect to remain free on the iPhone, but look out for at&t trying to prey on stupid people by selling them additional gps apps.