I have used idea cellular mobile sim for about a year and I felt it was pathetic. There were signal problems, internet issues, the customer care persons not responding accordingly and many more problems.
And not to forget the voice during the calls was not good as well. I dont think there is one good reason why I should tell you to go get idea.
But surprisingly the idea cellular association never bother about all these complaints they just want to eat peoples money introducing some stupid plans and activating them without knowing to the user. And adding to that the stupid advertizements they show everywhere on tv's , phones , internet etc. If there was 50% truth which they show in their ads the company would be on top.