Finally! A First Person Shooter where you are free to explore. What I like most about this game is the free form nature of it. You are (almost free) from exploring the entire world if you so please if it weren't for those darn radiated areas. The shootouts in this game are excellent as well as the enemy attempt to flank you as you and him can both die to a lethal shot. One wrong move and your existance will become pointless. What I don't like about this game is how buggy it may seem. Sometimes the AI doesn't necessarily follow you correctly or sometimes it randomly crashes you back to your desktop and the steep learning curve. You're thrown into the thick of 'the zone' and you must adapt survive and fend for yourself.
What others may fail to tell you is how frightening this game is. I'm not a coward, I played through doom 3 when it first came out and only screamed once! At points (fortunately not frequent) STALKER gets you with shock scares as well as a true sense of fear as you can hear mutated 'human's roam the halls of underground bunkers. The only thing that is keeping me from fully enjoying the game is its genuinely freaky sections.
Other than these flaws, and the coward that I am, I would only think that people who are fans of FPSRPGs with inventorys or people who like a good scare from their game will like this game.