Currently I am using Airtel 4G and I had very good experience with it.
I had never loss signal at any time or at any place, the signal strength is good.
Even in the packed room also I get the good signal.
The internet speed is good and surfing is very fast.The cost of internet pack is I think to high as compared to other operator.So I am not using the internet in Airtel, but the internet experience is great.