This video is horrible, it is nothing like Operation Flashpoint at all. There is even an exploding barrel at 03:39 in the video.
They should have named the game "Action : USA vs China, fight for Skira Island !".
The main difference between easy and hard mode is the absence of the HUD and the one bullet kill, but it will still play arcadey.
Arma II looks superb though and the gameplay is excellent.