I am using Idea service from the past 12 years. I have never got any problems from using this service.Idea provides good customer care support but wait to receive calls for problem solving.
The network coverage of this service is very good as compare to other operators.Apart from this there is no issues on roaming I went many time out of state but its never troubled to me.The post paid service is also good.
Idea is only few issues, The most is the pricing issues i.e little bit higher than other operators, and internet service is also costly.