I made a lot of changes in v3. I pretty much changed some civs into other civs. Heres the list:
Portuguese --> Saracens
French --> Franks
Dutch --> Byzantines
Iroquois --> Incas
Ottomans --> Turks
Most civs also got new units, you'll have to play to find out which civs get what :D
The center is a new feature, it allows players to capture it and within the center there is a base that you can train units from. This adds new strategies.
Another main feature is everyone has their own base. While this may seem like bad for defense, there is a 2 layer wall and moat they must pass to defeat you.