I was going to post about this in the stalker 2 thread, hitting on the idea of what I thought their mmo would hopefully turn out like (in a general sense.)
I've known about this mod for a week or so but only got around to playing it for a few minutes last night. The server was in it's night to dawn cycle and having no friends to play with (I'm a loser irl and online), I was afraid to go into any buildings to find loot or really do anything for that matter.
They play on subtle music and ambient noise pretty well for added atmosphere, though I wonder if taking at least the ambient music out would add to the experience. I'll have to play more but it seems like if you're playing on your own, it might be a more immersive experience. Playing with your buddies, you can make it into a big joke if you wanted.