vast improvement?? I looks almost exactly like the original, only with slightly better graphics and it seems the enemies responds a little to being hit now, that really the only difference I see..
Let's use our eyes and watch the video.
The first thing you notice, beyond the graphical improvements, is the animation has really become a lot better. Mass Effect 1 had the same problem a lot of RTC RPGs had, which is that it felt like you were playing a game of chess from the viewpoint of a pawn - characters practically slid instead of moved. Strafing and backpedaling looked ridiculous, the slow-motion run of the husks was comical, and everybody stood up straight all the time. The animations here are more fluid and dynamic.
The second thing you notice is the reactions of the characters, which you noted. Combat looks much faster-paced.
The third thing you notice is that weapons, at least the ones the PC is using, are off of the tiring battery system and actually have ammunition counts now. Gunplay in general just looks more satisfying.