With the risk of being called unpatriotic, this is my opinion ...
Only once I have flown AI (Mumbai-NY) during my 9yrs in US. When compared to that flight, the only other AI flight (domestic) that I have undertaken seemed far far better! That domestic flight was way back in Jan. 93 and was excellent to the point where AirHostesses (flight attendants to be politically correct) were smiling and were willing to happily assist me with mundane things like a missing pair of headphones! I think it is safe to say "forget it" now.
But, this BOM-JFK flight was a disaster from the start. To start with, the flight was delayed by 5 hours! The whole plane (747-400) rattled like crazy on take off! The seats were unbelievably crammed, even by economy class standards!!!
And to top that, the tail was shaking like crazy, as if it was about to come off! This isn't a gentle toss here and there but a constant up-down and side-to-side rattle that without holding on to the seats' head-rests it was impossible to walk to the lavatory and back.
The flight attendant couldn't smile if their life depended on it (probably she was a trainee).
The food was ok, nothing to complain there.
But, someone's comfort was that AI is better for our parents as some of them have difficulty understanding english. What I observed during my IAD-BOM Delta flight was that the Frankfurt-BOM leg was serviced by an all-Desi cabin crew; 20s flight attendants, smiling & helpful.
And what I have heard about AI is, when it is good, it is good! But, when it is bad, it is unbearable! This is from many friends and relatives who have flown AI, missed the connections quite a few times and have had a horrible time during the journey.