AT&T 3G Microcell Launched in Charlotte area.
The difference is that AT&T Microcell is a 3G service cell that sits at home connected to your broadband service.
The device works only in AT&T service areas and that is verified with GPS location service and you might need an extra long Ethernet cable as you might need to take it to a place where GPS satellites are visible, like a window!
In Charlotte, the device costs $150 ( that comes to $12.50 a month) and the service is free, but I feel everything should be free to full service customers.
Less Bars at home is not users fault, it is AT&T's for not having enough cell towers!
You can check if it is available in your area here.