Honestly, not worth it. First AC carriages have largely remained unchanged for quite some time while the advent of flights have made the price of first AC MORE expensive than flights usually for the same route. And unless, they provide the luxury given in the Maharaja express, it's nobody's first preference. Many folks going in this tier are sponsored by their company or discounted tickets or railways quotas. Few people pay out of their own pockets the cost of this when flights have become more accessible.
The one route where it...
more... is popular is for night time trains connecting two cities[think Lucknow Mail, Bangalore Mail, Darjeeling Mail].