Looks good, but I'm going to miss a few things from AC3. The first one being the size and foliage of the Frontier and animals within it. I liked the hunting aspects of AC3 and the urban areas of the previous games (doesn't look like either will be as big in AC4). I also get a vibe that this is an Assassin's game without much a purpose (kind of like AC Brotherhood and Revelations). I'll be curious to see how they tie this game in with the main story line.
Honestly I feel this really should have been a continuation of Conner's story. A Native American Assassin was a great concept that was just poorly executed. They just chose the wrong voice actor and the wrong personality for Conner. It's just hard to get excited about Edward knowing how everything ends up.