Apple's new iPhone firmware, iPhone 2.0 Beta 5, has a hidden option for enabling or disabling 3G. Disabling 3G allows the user to increase battery life at a cost of lower bandwidth throughput. It also appears that Apple will be using the same firmware for both existing iPhone models and the new 3G iPhone models; however, of course you will need a new 3G model to see or activate the hidden 3G setting.