The big thing is the "openness" of the game's world. The world is vast and from the map, looks like it covers pretty much the entirety of Cuba and the Dominican Republic area and a bit of the surrounding. Due to this there is also a large reliability on the Jackdaw, Edward's ship, to navigate around. This is also not via "instances" or a required load mind you, but a seamless movement just as if you were riding a horse and dismounted. Really cool and fun to watch.
The video also pin points on a few of the mechanics and collectibles of the game. There is a free aim feature now. You gun nuts can now use your CoD or Battlefield skills to help with assassinations in the game now whereas before it was close range and lock-on. As far as collectibles go, we get to look out for Sea Shanties as well as the normal mix of items that are staples of the AC franchise. In the video you can kind of hear one, but now I have to get my own real world collection together to see if I personally know any that I can sing along to.
Outside of that it is just more of the game world and standard mechanics being shown off. Everything looks amazing and looks like care was taken with bringing what we know with a mix of new mechanics to keep things fresh. I guess we'll know for sure on October 29th.
