I own stalker but haven't played it much more than a couple hours.
Someone posted this link in another thread to
Stalker CompleteIts a mod that improves a lot things on the game, mostly graphics.
The description excites me:
It was designed by professional graphic artists with rich experience in the field, following industry standards for creating interactive 3D environments. It features artistic works and modifications from many community members unified under one art direction.
[...]
Natural lighting, vast panoramic views, depth of field, parallax mapping, SSAO, over 900 reworked texture files, including vehicles and armor suites with manual bump editing, you won't believe it's the same game.
And thats just part of the stuff listed.
I'm thinking of using that for my first time playthrough.