It’s important that the developers should explain the concept behind any change so that when the end user gets the product, the difference can be felt. BioWare obviously is bringing some changes in Mass Effect 3 which will differentiate it from the predecessors and they want to pin point these changes. The footage below is about Combat Mechanics, Improved AI and Class specific features.
So AI now will be wiser and you will have to wait for the openings to execute the attacks properly. Class specific features is another major advancement in the series which means that every commander Shepard will be different this time depending upon the class you select.
Mass Effect 3 will hit stores in March, 2012.