I have travelled by all the domestic airlines multiple times. Before starting, let me tell you, my journey 90% of the time is Bangalore <--> Delhi. I think Indian Airlines is the best among all the domestic airlineses.
Here are few data points, step by step:
Fare: People normally have misconception that IA is very costly, even I too had this perception. But, if you check the price a week before or 2-3 days beofore of your journey, you will find sometimes it has the least fare (even compared to low cost airlines like Air Deccan, SpiceJet). I have seen it myself many times. Here is the key: If you plan your travel much before your travel date or on the day when the booking opens for low-cost airlines you would definitely get the lowest fares, but if that is not the case IA is definitely a good option.
Check-In: You can feel the difference from here itself. On Delhi you have different terminus for IA. The one for all the others is pretty croweded. Rest all is same, but I personally don’t like Air Deccan Check-In.
Flight Attendents: If you give more weightage to the faces of flight attendants then KingFifher is the best. But if care is the one which you care most then this is the flight. I had a fracture is my right hand and they helped me a lot with delication and affection. But, I didn’ see the same thing in Jet Airways attendants.
Seating Space: If you are taking late morning or noon flights you will find more space, otherwise it is similar to others.
Punctuality: Not to say anything about, it is no doubt a very important aspect of flight, where IA beats everybody else except Jet Airways. Air Deccan, Air Sahara are pathetic.
Security and Reliability: This is more of self saticfaction and depends on your thinking. I feel a bit more secure in IA thinking that it’s crew is more experienced and thus can be trusted. I remember there was something in newspaper about a training which happened last year winter for Pilot and crew members for landing/taking-off during fog, the Air Deccan did not take it and then it was made mandatory by Government.
Overall it is a nice experience to fly with Indian Airlines.