The first thing that comes to my mind... This will be a huge sell argument for Android: "Buy Amazon books 25% cheaper than on Apple phones".
Oh, yes, because of course, cell providers whose phones run Android would never think of charging any kind of data tariff or making money in other ways.
That is, so long as net neutrality remains. If they start doing packet introspection and charging based on destination or traffic type, well, that is going to be bad for all mobile users.