A few previews of S.T.A.L.K.E.R.: Shadow of Chernobyl recently.

Firstly a mulitplayer hands on with gamespot, including a small video.

The multiplayer game will incorporate the day-night cycle that's in the single-player game, so the sun will rise and set during a match. The designers are still discussing whether to make it an accelerated time cycle so that you'll see a day pass over the course of approximately 20 minutes

Secondly, ign also has a hands on preview of the game.

Even though S.T.A.L.K.E.R. is a first-person shooter, it contains a lot of role-playing elements similar to Deus-Ex.