Having played the scenario 3 times, I'll weigh in on the DLC.
General Information
The scenario pits the Old World (Spain, England, France) against the New World (Iroquois, Inca, Aztecs). The scenario uses a dynamic map with a different version of the new world each spawn. The geography of the New World is not historically accurate. A nation wins the scenario by having the highest score after 100 turns. Custom rules give bonus points to certain events, such as finding China or returning New World treasure to the Old World.
Game #1: Spain
After unsuccessfully finding info about the scenario in this thread, I started a game unprepared as Spain. My caravel made a beeline for the southern tip of America in hopes of finding China first. The geography seemed a bit incorrect, but I assumed that it was different to balance certain historical islands. Soon enough I found my caravel blocked by ice and killed by scurvy (a unit promotion that slowly kills your unit while out of friendly waters). Realizing my error I decided to quit the game and try again.
Game #2: Iroquois
Playing as Hiawatha, I quickly expanded and developed techs. During this game I realized that the New World continent was random, and that either the north or south passage would be open to China. I did not build a caravel. When France settled near me I immediately declared war (too soon). With too few soldiers to take the French city (2 archers, several spearmen) France had time to build walls and defending units. Despite this, my tech rush and quick expansion yielded catapults and horsemen, allowing me to defeat the french city. They sued for peace and I agreed, noting a second french city south of my territory. I used the 10 peaceful turns to move my army south and declare war again. I took this second city and declared peace. With 10 cities and a large army I was the undisputed master of the continent and no Old World cities were present. Meanwhile, the English settled on some northern islands while the Spanish settled Aztecs lands on the southern continent and fought a protracted war. The Incans sailed for China. In the end, The Incans beat me by a score of 705 to 698. Their 3 China boats yielded too many points (IMO). I think it was 150-100-50, but I can't remember exactly.
Game #3: France
This time I played as France and determined to use the French city-state bonus (and my social policies) to secure and keep allies. I sent one caravel north and one south. Finding the north route open, I immediately built 2 more caravels and sailed to China. I won all China points. (England had a boat ahead of my 3rd caravel, but they died of scurvy near China's borders). Meanwhile, I settled 2 cities on the nearest portion of the New World. I made allies with 2 militaristic city states, who supplied me with the bulk of my army. One city's borders included one of the special 'treasure landmarks' which periodically spawned a treasure unit. I finished the research tree in this game, (obtaining piracy) and eventually fought a war with Spain. I captured all of their colonies. I won by a large margin in this game, being the 2nd or 3rd strongest world nation and having won most of the china/treasure points.
Overall Evaluation
Pros: I had fun playing this scenario. It presented me with very different games each time that I played it. It was error-free and as historically accurate as possible. While purists might argue that without a proper map it cannot be accurate, I argue that exploration was a crucial part of the era - making a known map an incredible advantage for the player. This scenario should work very well as a fun and quick multiplayer game (although I have not yet played multiplayer ciV).
Cons: I feel that it was overpriced; 2-5$ would have been more acceptable. The idea of the scenario was well-conceived, but lacked specific features that would make it worthy of purchase. For example, the tech tree should have been expanded to provide more historical units and techs (ie: early firearms). In addition, the European powers were too similar. They had no unique units or buildings, but they shared several units like the musketeer, tercio, and conquistador. I would have liked to see religion included in some way. I was surprised that the Dutch were not included (as they were instrumental in early American trade).
Final Thought: If you have been waiting for a high-quality, historical scenario, but have found most of the community-created scenarios lacking, then I recommend you purchase this DLC. I received my money's worth. If you don't want to pay for any additional content - do not buy this DLC. While I preferred the Mongolian scenario in many ways, I don't feel that it had much replay value. Having played this scenario 3 times, I will still play it twice more (to test the Incan and Spanish civs). This is the best scenario for CiV that I have played thus far.
My Rating: 
(6/10)
Enjoyed the Mongol scenario? Me too! I just don't see many chances for replay since you cannot select any civ besides Mongolia.
). As it has been said, European countries don't have specific UUs or UBs, just their UA (France UA is changed to that of Alexander). Tercios, Conquistadors, musketeers, privateers, etc are available to Americans too if they research the ends of the tech tree; there is a "future tech" too, which gives a great deal of points (I was a close second in the 700s, and the difference jumped to around 200pts), but don't expect to research it by normal means (i.e., without a great scientist, or the Oxford University) 
