I am using airtel for more than two year . On that basis I would recommend this network for all .
I have visited many cities of india and I found that, it may happen that its signal way tend to become weak at some location but you will rarely be in a situation where there is no network.
I would especially recommend it for professionals that can pay more money but dislikes bisturbance between calls .
AND if you have dual sim phone then its a must.