Really airtel is the best smartphone network. I am using its 3g service and its network speed is superb. You can find it anywhere its network coverage are available. On airtel network its voice calling sounds are digital. No issue with its service.
There are less billing issues in comparison to others. For me the services are best Indian telecom industry. Awaiting for the 4g services to be launched in my hometown, hope that it would be good and feasible as the 3g network it offers.