While the rates from India to other destinations look good and can save significant amounts, the rates from US to India mentioned are not attarctive.
There are a number of Calling card companies (Reliance being one of the better ones for India calls) that offer cheaper rates and they have the additional advantage that you can call from Phone-to-phone and not depend on a PC with internet availability.
Even in India, if you add the cost of internet, it may not be as attarctive unless the user needs internet for other purposes.
So, the technology is there, but not yet smooth enough and not always cost-effective.
