In the Assassin's Creed 3 gameplay video from E3, Ubisoft Creative Director Alex Hutchinson discusses some of the new gameplay elements that will set AC3 apart from the rest of the games in the series.
Assassins Creed 3 marks the first appearance of a new protagonist, Connor Kenway, who is half European and half Native American. Unlike Ezio and Altair, Connor roams through the forests of the Mohawk Valley instead of an urban setting. So instead of climbing buildings, he will climb cliffs and trees.
Hutchinson mentions that this would be a good time for anyone who hasn't played an AC game to jump in. Listen to the man. If you haven't gotten into this series yet, for the love of Ezio jump in now.