I found 3 nice videos made by tweakguides.com you can view them below and read his short paragraph on what he thinks about the game.

"My initial impressions of the new FPS/RPG game STALKER: Shadow of Chernobyl are that it seems quite atmospheric, with a relatively large, open, non-linear world similar in some ways to Oblivion. You have a fair bit of freedom in choosing who you side with, which tasks you undertake and whether you want to play the game at a fast or slow pace."

To read the full article head over to his site here

Stalker Game Play Video 1

Stalker Game Play Video 2

Day Night Comparison