S.T.A.L.K.E.R.: Clear Sky - E3 Preview @ Gamespot

This appears to be one E3 preview we haven't got around to yet. Gamespot does a hands-on with the Clear Sky prequel from GSC Gameworld :

There are several factions in the Clear Sky universe, and allying yourself with one (or more) will open up squad support during hairy missions. On a dark street, Scar[the player character] stumbled upon a renegade, and our squad held him at gunpoint. The rogue said he had information that would be valuable on the road ahead, and he would gladly give it in exchange for a medkit. Since our faction isn't one to give in to such demands, this rogue was unceremoniously gunned down in the street. There are plenty of choices like this in Clear Sky, and deciding who lives or dies will alter your story experience in this dynamic world...