IndiGo, the name itself tells you what the airline is trying to achieve. Neverthless, I flew with this airline in their infancy period i.e. when they started their operations in 2006. I flew delhi to bangalore and back to delhi and the experience was quite satisfactory given the fact, I have flown with most of the domestic airlines in india(except kingfisher).
Only airline, I would rate better than IndiGo is spice-jet at the moment. Please note that I am talking about low-cost airlines here. IndiGo might have started giving snacks etc(not sure), but at the time I flew with them, it was serving only candies and water which was expected because of their rock-bottom fares.
Who can expect to fly from delhi to bangalore for 2000 bucks(including taxes). I flew with them again once in december and things hadn’t changed much. Booking tickets is also easier as their website design is quite good.