I consider Reliance India Call the best thing happened to me last year. I use this calling card service from Reliance to call India almost everyday. The connection I get is very clear and I never had any problems with it so far. They don't charge any connection charges or fees. I use the prepaid option and usually buy $25 worth of calling card each time.
They started out with this service some time in August 2004. At that time they charged 10.9 cents per minute for calls to India. They later raised this fee to 12.9 center per minute. Although there are some other calling cards available with lower fees, their service is not as superior as reliance's.
I have experimented calling cards from bigzoo, which went out of business; 9278.com, and EnjoyPrepaid.com. I would rank reliance first, then enjoy prepaid and then 9278.com.
It is very good to see that a company which started out in oil refining business is now carrying telecom traffic from US to India on its state of the art global network. I believe Reliance is like GE of United States.