It's just an addon!!!
Don't get me wrong it's always nice to have the same enviroment in a new sequel but there has to be some changes. The only change I can see from MW2 is the Ambient Occlusion so far, some acoustics changes which I liked the old ones in MW2 better. If you ask me they have done it real bad. What a shame it could have been a lot better. The only good thing I can think of, is that you can max out the settings & still max the frame rate cause it doesn't utilize the new generation video cards technology. I bet they will come up with a game later on that will bring any modern PC to its knees, just to make it up.
5 out of 10 is the best score