Its okay if you enjoy naval combat.However other then that it doesn't add that much into the game.
It really adds alot to the Eastern Asia region, turning it into a more intresting region and gives the game more replay value.
A good DLC if you're into doomsday scenarios, however other then that it doesn't add much for people that just want to build a nice city.
Want to make your cities more green and beautiful?Then Parklife is the DLC for you.
Mass Transit is a great DLC, it solves traffic problems and adds new ways of transportation for your city.