Apple has begun selling unlocked GSM iPhone 4s in the US. The move was expected but the timing is strange as AT&T lost its exclusivity over the iPhone 4 earlier this year.
Prices for the unlocked iPhone 4 start at $649 for the 16GB model and and $749 for 32GB. The CDMA iPhone is not available unlocked.
On the store Apple outlines in detail what an unlocked GSM handset means for those buying, outlinging the advantages over being able to choose their own carrier.
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.