I just came back from a trip to India and flew DN. Before booking I was aware of their notorious reputation for being late. However just before booking I noted an ad that said that the punctuality was improving and was 98.7% for Oct. I believed and made the booking only to regret. After I landed in india and told my folks I was flying DN they laughed and told me to buy a cell and watch for constant SMS's regarding "re-scheduling". My flight was delayed by 2 hours. Another relative said that the ad was based on flight times using the "rescheduled" timings and not the original time. I just can't believe authorities could allow such false advertising.

My 2cents: if your point of entry is BOM and looking to fly to your main destination it would be safe to book a DN flight from BOM - destination, but for your return assuming you are flying out of BOM the same day, fork over the extra and fly a more dependable airline so that you don't miss your connection. Delays of 5-6 hours are quite possible.