i can never be tired of the demo i gonna buy the game.I've played each mission 4 times atleast. I've shot, sniped, slashed, strangled etc. each and every one of my targets. Thats how open ended the gameplay is... U wont find so many different ways to kill in any other game.

The AI is pretty good at the NORMAL skill level... very rarely do they act ridiculously dumb.
You are accountable for every action in the game... for instance if you get caught on camera (which you will pretty regularly), you're gonna have to steal the security tape from the guard quarters. Not doing so will affect your rating and your future missions.