I haven't read everyone's post about the audio, but have you noticed that when you issue a command, have a response from AI or friendly, or Voice Chat with someone on comms, and you are in a building you will hear the response slightly echo as if you are in an empty room? If they are in the same room of course. If you issue a command in a building it will echo as if you are really in there? Cool little touch I like. Try it in the hangars on the first Infiltration map.
Also if you are charging a door and have to get in quick, standing up and running, hit your use key as you get to the door and you will kick it in.