Cod4 Forums has gathered a lot of info to do with COD4. The info comes from magazine articles, interviews and anything else that has let slip some of the games details.
This is part of the article:
- Experince Based Progression - Unlockable Player Customization - Unlockable Weapon Customization - Unlockable Equipment - Ability to call in airstrikes - Ability to man Vehicles - Ranks are sorted as experience-based progressions
- Ability to fly aircraft at some point - All Cut Scenes in 1st Person - Episodic Storyline - Missions split into days - Very cinematic feel - British SAS playable - U.S. Marine Corps 'Force Recon' playable - Captain Price is back!! - Slimmed down HUD - Will spawn 15 seconds after death
- IW in-house engine, possible with rag doll effect - Incredible Physics - Destructible Environment - Fast load times - Rim Lighting - Depth of Field - Ability to shoot through some materials - Accurate Nigh Vision - "Eyes" adjust to light over time - 60fps