Saw this game on my mate's PS3 last night. Was suitably impressed by the long cutscenes, we only got about 5 minutes into the game so I can't really vouch for the gameplay.
One question though, what the hell is up with those strange adverts at the beginning?
They are the Beauty and the Beast corp. You figure this out as you play the game.
Whats really great about MGS4 is that you can choose to play the game with stealth or all out gun blazing attack as opposed to previous versions that were definitely more stealth. In fact there are numerous ratings in the form of type of animal depending how you played the game. I ended up with 'hawk'.
This is definitely the more cerebral gamers 'game' with a plot and theme tied into the game.