We need some background noise (people talking, laughing, coughing, etc...) when you enter a large group of people. That would really help add a lot to the atmosphere of the game in my opinion. Now all you hear are buffs being cast, footsteps, and weapon noise.
AC had this, and it was really cool... it added a lot to the atmosphere when you entered a town/village. You'd hear the sound of general conversation.. a woman laughing occasionally or what have you. As nice as it was, it was still static, though. AO could improve upon the idea by making the noise scale to the number of people in the local area. The mission terminals in Newland could be a REALLY noise place.
I dunno, just an idea.