Forget everything you have ever learned from anarcheous first person blood-bath games.  You will need a totally different strategy for this game because when you're dead ... well you're dead.  You can't just reappear and  keep playing.  One shot + one kill = Realism.  You will have your back  against the wall, waiting to peek around the corner without making too much  noise.  Your heart will race and the adrenaline will flow as the dramatic  music heightens the suspense of who lies around the corner, or behind the  closed door ahead.  You will dim the lighting in your room and turn  everything else off so you can hear which direction the footsteps or the  gunshots are coming from.  You will be surprised, scared, shot from behind,  sniped, outnumbered or out-shot.  The replay value is extremely high  because of the online play, terrorist hunt, and lone wolf options.  Some  missions are nearly impossible on the highest difficulty setting which can  get very frustrating.  The online play is VERY addictive because getting  killed is more cause for revenge than getting fragged.  I would recommend  getting the expansion pack as well because of the custom mission option.  This option creates at least another month of replay value alone.  Can you  strike hard and quietly enough, without being seen and alerting the  hostages all at the same time?  It's up to you to find out!