After spending 3 anxious hours waiting for the demo to download I finally got my hands on the demo of Cod4. Well I can say yes, yes it does live up to the hype. It feels just like the other Cod's did with intense battles and great sound and graphics. There are some subtle differences which really improve the game. For example while the game is loading it plays a sort of military briefing video so it doesn't really feel like a load screen at all. Also the player has the ability to throw grenades back , something the AI could do in previous game but we couldn't. The combat is even more intense then before. I know you're wondering how that's possible but it really is. Bullets flying in all directions and RPG's flying past really gives you a sense of immediacy. The graphical improvements really help with this. There's heat blurring and a field of view effect. Also the whole stage looks very "bombed out" and feels like a warzone.
All in all it looks as though Cod4 is going to turn out to be a great game that really improves the Call of Duty series.