Bioware just released this latest video outlining some of the new features expected to be present in Mass Effect 2. Some of the important highlights of this video are :
1. Mass Effect 2 will feature bigger world and more exploration than found in the orginal.
2. Smarter Enemies with better AI will be present in the sequel.
3. If you have saves from Mass Effect, those will ultimately effect the plot in Mass Effect 2.
4. The game will be demoed at E3 2009 and the game will be playable at the event.
Update: This video is no longer available.
