I can confirm on that Airtel does rock. With my experience any problem [I have had 2 problems in total with Airtel in I think >5yrs now] average fixing time is less than 12 hours.
Reliance, I was with Reliance - at that time they had a reputation of cheating their customers by overbilling.
So Yes Airtel Rocks, and I dont mind to may a little extra for the Fantastic Service they provide.