As of last week, Apple now offers the iPhone 4 in three flavors: the AT&T iPhone 4, the Verizon iPhone 4, and the unlocked iPhone 4. The unlocked iPhone 4 can be used with phone service from any GSM carrier, and you can install apps not available from the App Store.
People have been unlocking iPhones for years, but an officially unlocked iPhone means that the device won’t risk being “locked out” from iPhone operating system updates.
Should you consider buying the unlocked iPhone?
The answer is “yes” if you plan on traveling overseas or if you think you will need to change GSM carrier and don’t want to be stuck in a two-year contract with AT&T or Verizon. You can find out more from this CNET article by Josh Lowensohn.