Users who have used the latest iPhone 3G firmware say that the device will have support for over the air firmware upgrades and FM radio support of some kind.
The FM radio support means that the new firmware would let iPhone users use the iPod Radio Remote along with other accessories that will let users listen to regular FM radio with their iPhones. Currently the iPhone and iPod Touch are incompatible with the radio remote.
Firmware over the air means that Apple or AT&T would be able to push firmware updates to iPhone users, theoretically to help fight against users of jailbroken and unlocked iPhones.