Air tell is one of the popular operator in India.
Iam using it from last 6 years and found that at start it was akittle expencive when airtell provides only 350 sms in 35 rupees but as time gone . Airtel became a good network and now airtel is providing good packs for mobile prepaid and for postpaid also.
The major issue in Uttarakhand as I am a citizen of uttrakhand when we go to hilly areas most of the networks dont work there but airtel do and it works so good
As I know air is very good in bageshwar, almora and moreover pithoragarh which is at the end of the hills and there is no network problem with air tell sone places are yet to cover but it works properly.
And 3g and 4 g services are good to use in hilly areas to. Even in himachal air tell do work very well.