Update: Best offer on Aircel is Free Aircel to aircel calls + 800 minutes local/std to others.
Aircel is giving away unlimited Aircel to Aircel calls in Rs.149 in Delhi which is far less than competition as they are yet to launch all calls free voucher. Like Jio 4G is offering unlimited calls in Rs.149 after 31st march 2016. While Rcom is giving away unlimited free calls for 90days in Rs.501 only. Bsnl has promised Rs.149 voucher from 1st Jan 2017. Airtel is giving unlimited calls in 299 with 1.25GB-3GB 3G data as best offer. 
Comparing to all above only Aircel to Aircel calls free that too local seems so very less in response to competition as they are yet to launch unlimited calls to any number free voucher.
Problem is Aircel Delhi is 1800mhz which is not optimal for in-building coverage. Their 3G service is on Rcom and Vodafone network where most of STV for voice doesn’t work. Calls to landline are 3p/sec regardless of STV you use.
So unless you need for secondary no for cheap voice calls which now also sounds remote possibility with Jio free voice calls I don’t see why would anyone opt for Aircel mobile services in Delhi. The one who are using are unaware or too lazy to port out.