The primary focus has been on the iPhone 5 and its availability on the major carriers here in the US on September 21st. However, smaller regional carriers such as Cricket Communications and C Spire Wireless will be carrying the iPhone 5 a week later on September 28th.
C Spire was the first regional carrier to offer the iPhone, when they rolled out the device last November. Cricket on the other hand, was the first carrier to offer the iPhone on a prepaid basis. Cricket introduced the iPhone on their network in June. Other regional carriers, including Appalachian Wireless, Bluegrass Cellular, Cellcom, and GCI will be offering the iPhone 5 on September 28th as well.
I think this is a good thing. It puts competitive pressure on the bigger carriers, while also offering the device to people in different markets. I can see, for instance, a college student who presumably has little cash on hand, snapping up an iPhone on Cricket.