A game like this is a rare gem, (or artifact!) that should be explored, researched and enjoyed to the last bit!
You are a STALKER, or a scavenger, going into the forbidden quarantine area known as the Zone, looking to get rich. You get to see mutated creatures, radioactive areas, mercenaries and of course you get to shoot your gun. Enemy AI is quite good, enemy soldiers flank you, surround you, and do headshots (that is, you can have most of your health and then die all of the sudden), the mutated creatures mob you, stalk you, and scare the bejesus out of you too. The areas are quite vast, though not as big as Oblivion or Morrowind for that matter, but considering the story takes place in a relatively small area, it’s well done.
The sound is another element that makes this game great, I just love when idle fellow stalkers just sit by the fire, pull out a guitar and start playing, as if they were knowing their dire situation and are just saddling up for whatever comes. The guns: well here's the thing, they don't shoot that well, in fact they shoot very realist rounds! Anyone that has ever shot a gun at the range, knows that a doing a headshot is very hard, and in this game to get a headshot is VERY hard, you can either get a really accurate gun (like the dragunov) or get lucky in order to score them.
Story: Well imagine your mission is to get into the site of a nuclear accident in order to get rich with whatever you can find, and in the way uncover the secret at the Chernobyl Power plant, with a well detailed and accurate world and you get Game of the Year material.
Bugs: Of course there are. Not game killing mind you, but they are there.
So in the end if you feel compelled to get the game after you've read this attempt at reviewing, go for it, you won't be disappointed. And if you are into history too, check out wikipedia or other online sources about the Chernobyl disaster.