Assassin's Creed Brotherhood had a single-player trailer for E3 - with commentary from associate producer Jean-François Boivin. It's all good stuff...
Not only does Ezio get stopped in mid connubial, we're also told about new weapons, new attack modes and that, "We're going to exploit the full potential of the horse... a horse will play a major role in missions and free-roaming and now be used in acrobatic sequences as well as in advanced combat."
Also, more gadgets because, "Ezio will have multiple new gadgets and machinery at his disposal."
Add to this the fact that the "Fight system changed in favour of those who move first and move fast, and enemies will now attack in multiples."
Enjoy.