AT&T’s CallVantage will have a softphone courtesy of CounterPath.
This is a great move and it will begin a movement by mobile operators and other VoIP carriers follow suit. Already Earthlink has Mindspring that does this as does Vonage which has had a softphone for almost as long as they have been around.
The difference here is it’s AT&T putting its mark on what a lot of people already know is proven way to communicate.