What it does though is enable synergies and an exponential amount of strategies. It also greatly affects the entire playthrough of the game.
For instance, let's say that you want to grab land quickly and so choose the liberty tree with its free settler. The weakness of this is that you end up short on food and culture and happiness. Well, you can choose traits that enhance the food, culture, and happiness, and so alieviate this shortcoming.
Or, you want a small traditional kingdom. They do okay in the short term, but mid-game a lack of territory will see you falling behind. But if you choose a religion that gives you gold for every foreign city that converts to your religion, then you can have your little kingdom while conquering the world with your religion and becoming rich in the process.
Or you can go the secular route. The new faith additions require lots of buildings and you can eschew this for an advantage over your opponents.
There are many more combinations that are possible. It effectively makes for many different paths of victory to try out. The original game, I felt, had only a few paths to victory, and so this is a big improvement.
There are other gameplay enhancements. Hit points are now 100. This is important because previously, all attacks did a minimum of 1/10 damage. So you could take down a powerful tank with 10 attacks from piddling archers. Ships are divided between melee and range. This makes a navy worthwhile. Previous civ games saw me making zero ships, since land units were the only ones that really mattered since Civ is all about cities.
Now, ships can capture cities. They can capture other ships.
This alone makes civilizations like England viable, unlike the original game. England receives a +2 movement bonus for ships. Since ships were nearly useless in the original game, and at best were geographically limited artillery units, England's +2 movement was a waste. But now, England can threaten any coastal city in the world.
AND, simultaneously, this makes the commerce culture tree much more useful since commerce has a handy little talent that gives you +3 production in coastal cities.
There have been some tweaks to the tech tree and new civilizations too. They seem interesting and I've yet to figure them all out.
All in all, if you are a civilization V player, this is an essential purchase. It makes the game much much better, for what it is.
Release Date June 19, 2012
Developer Firaxis Games
Publisher 2K Games
Controls Keyboard, Mouse
Flags Expansion Pack