This seems like it's good for the riders (they pay less), for the environment (more people traveling in each vehicle), and the cab drivers (larger total fare). However, since it's decreasing the demand for taxicab trips, some cabbies are complaining:
“Every additional passenger that gets into one cab, that means a second cab is left empty,” said Bhairavi Desai, executive director of the New York Taxi Workers Alliance. “It’s horrible to implement a program like this in such hard economic times.”While it's arguably bad for some drivers, it is very good for passengers, so the second argument doesn't make a lot of sense (except that in general, midtown taxi riders earn more money than taxi drivers).
What is interesting about this new plan is that the fare is not particularly higher than the $2.25 single ride on buses or subways operated by the MTA. So if there's such demand, I'd think the MTA could start running 8-to-13-passenger vans along these routes just charge the $2.25 base fare. Once you start adding more people to the vehicle, all the starting and stopping starts to add delays, but I bet most people are just going the full distance anyway so they could eliminate the midway stops.