* : If you choose to use your unlocked iPhone with AT&T, you can pay for your service on a month to month basis. Contract lock-in is only required when you're buying a carrier-locked phone. So if a two-year commitment give you the willies, this may be your way out.

* : We admit that this point has become less compelling ever since arrived earlier this year, and gave U.S. iPhone users a choice of carriers. Still, if you live in a part of the country the neither AT&T nor Verizon serve particularly well, you could pony up for an unlocked iPhone and try your luck with T-Mobile's network. (You couldn't use your unlocked phone on Sprint's CDMA-based network, incidentally--only GSM-compatible iPhones are available unlocked.)

* : We mentioned the price tag of an unlocked iPhone--$649 for the 16GB model and $749 for the 32GB version. That's quite a markup from the $199 and $299 you'd pay for the 16GB and 32GB iPhones with a two-year contract. And while the lower initial cost of the subsidized iPhone doesn't take into account what you're committing to pay AT&T and Verizon over the next 24 months, the price of an unlocked iPhone will still be too steep for some users.

And if you're hoping that you can get cheaper AT&T rates by purchasing an unlocked phone and, say, forgoing a data plan, we have bad news. AT&T spokesman Mark Siegel told that any iPhone on its network--including an unlocked iPhone--is required to use an iPhone data plan, the cheapest of which starts at $15 per month. Siegel said that when AT&T detects an iPhone without a data plan, they'll ask you to pony up for one, or terminate your service.