Apple has begun selling unlocked GSM iPhone 4 in the US. The 16GB black model starts at $649 and the 32GB $749. The unlocked device has all the features and can be used worldwide on supported GSM:
If you don’t want a multiyear service contract or if you prefer to use a local carrier when traveling abroad, the unlocked iPhone 4 is the best choice. It arrives without a micro-SIM card, so you’ll need an active micro-SIM card from any supported GSM carrier worldwide.
The unlocked iPhone 4 requires an active micro-SIM card that you obtain from a supported GSM wireless carrier. Simply insert the micro-SIM card into the slot on your iPhone, connect to your Mac or PC using the USB cable, and launch iTunes on your computer to complete the setup.

