What is The Matrix Online?
from the Matrix Online web faq, added comments by me.

This spring, the Matrix will become a reality when gamers everywhere log into The Matrix Online for the first time to continue the saga of the movie trilogy. Players of The Matrix Online (MxO) will inhabit an enormous urban sprawl, which spreads for miles in all directions. There are subways, nightclubs, skyscrapers, and dark alleys that all seem normal on the surface, but beneath this pedestrian exterior, a secret war is being waged for the survival of humanity and machine alike. Here, you and many operatives like yourself, will determine who shall inherit the earth.

Gameplay Highlights:

• Dozens of weapons and dramatic martial arts maneuvers that capture the "wire fu" Matrix experience. Use devastating special moves and sneak attacks including breath-taking bullet-time effects that are intelligently generated based on player moves and tactics. (One of the coolest parts of the game, in my opinion)
  
• Plot lines by the creators of The Matrix continue the Matrix story where the movie trilogy leaves off and provide you with deep insight into the world of the Matrix. (Plots will truely begin on April 4th. On two servers, the truce between man and machine will never be repaired once broken, while it will be storyline driven on the other servers)
  
• The Matrix Online will engage you with special events, missions, and monthly story cinematics, all of which effect the action in the game. (At the end of beta, the devs killed off Morpheus. It is unknown whether they plan something similar in the Live game)
  
• A full Rich World cityscape environment with traffic, living neighborhoods and breathtaking skylines that immerse players in the most authentic Matrix Mega City ever created (Using RichWorld technology™). (Very buggy. Currently video memory has a bad leak in it that goes overboard when this is turned on for me, at least. I wish I could see the city in full glory, but I cannot at this time.)
  
• A robust mission system designed for maximum re-playability and depth. Players receive missions from familiar organizations in the Matrix, such as Zion and the Machines. (This system is better than City of Heroes in the fact you actually choose what kind of mission and the distance travelled during it.)
  
• Authentic "Matrix style" clothing and character customization options allow players to live a virtual life that reflects the fashion of the Matrix movies. (Brings out the fashion designer in you)
  
• Find, create, or trade Matrix "ability code" that provides incredible knowledge and skill to your character. Unlike other massively multiplayer games, ability code can be swapped out and exchanged like trading cards, providing unprecedented flexibility in the development of a character. (The truely classless game allows for you to change direction and abilities whenever you desire.)
  
• Players can tap into sources of "information" in the game to create or steal code fragments. Code can be used to create both special Matrix items and special abilities. (Still has flaws, but is similar to tradeskilling in other MMOs)