The problem, of course, is that they're a) not any more open than they were yesterday or a month ago, and b) that they're just as open (or closed) as most other mobile networks. Ralph de la Vega, CEO of AT&T's wireless business says: "You can use any handset on our network you want. We don't prohibit it, or even police it." This is opposed to...what? Other mobile networks that somehow prohibit you to take their SIM and use it in any unlocked cell phone? Erm, I don't think so.
Furthermore, AT&T is not so "open" when it comes to the iPhone: you still need to sign the 2-year contract to use the device. "The iPhone is a very special, innovative case," says de la Vega. Well, I guess they might want to change those headlines to AT&T - the most open mobile network in the world, except when it's not.