I travelled on the new Newark-Mumbai route on Jet last month going to Chennai. The flight/service/food/entertainment were excellent, better than most other internation airlines I have travelled on. I would say it rivals or even beats Singapore airlines, one of my favorites.
Everything is fine if you are travelling to Mumbai. But if you are travelling to another destination as I was, you are in for a terrible time. The main problem is that almost all domestic flights in India fly only during the day and all international flights arrive in the night. So I had almost 7 hours at Mumbai. Getting to the domestic terminal was fine. But given that there are so few people travelling at night almost every place there was closed as was the airline lounges. Also the airport had too few chairs for the number of international travellers who were waiting for their domestic connections. So it turned out to be a horrifying 7 hours wait there.
On my return trip to the US the same happened when I had around 5 hours of wait at the international terminal and the lounge was so overflowing full due to the number of international flight (the airline industry is fireing on all cylinders in India), that it was hard to find even seating space there. Also there was so much confusion with gates being changed at the last minute resulting in hour long security queues. The flight was delayed by almost 1.5 hours due to non-availability of gates!!
So a lot more people are flying nowadays both domestically and on the international route. Airlines are improving to compete for these customers, but the airports are the same. Even after privatisation(the airports are much cleaner now though), the airports are not growing to keep up with the growth of passengers.
My future decisions on what flights I will take will depend on trying to eliminate connections inside India. So this maybe a stumbling block for the new Indian airlines trying to create international routes to India.