I have been a long time Aircel user ( for than 5 years) . Initially it was good however, later started experiencing many issues.
The main issue is the signal strength.
For all those who lives in Delhi, be careful. If you travel a lot, never buy it. If your house/office in the basement, dont get it. Also, the 2G/3G speeds are not that good. The plans are, however. Make a wise choice.