I live in ghaziabad, which comes under NCR region. I have tried almost all network service providers here. Airtel, idea, vodafone and now aircel. and I feel aircel is best of the lot here in terms of tariffs, plans and network coverage. network coverage is comparable to airtel and vodafone which are considered for best network in NCR.
I never had a requirement to call customer service so no experience could be shared on that perspective because I have not experienced any network problem in last 2 months except that it does not catch network inside my home anytime but that is only one area and I do not stay there most of the time. My experience with aircel has been awesome but I wish I had network coverage inside my home as well.
If you belong to NCR, you should definately consider aircel if you are planning to change.