About a week ago the E3-2007 build was leaked, I recently managed to grab a copy of this and have a play around with it.
I have to say, "X-Ray 1.5" is a far more polished engine even in it's current beta state than the shit that was released with shoc, my relatively mid-range gaming machine had no trouble at all reaching 60fps with everything turned on, and I still have some issues in the original stalker with framerates. The AI is much improved, they take cover and peak/lean around, run from and throw grenades properly. There really isn't much there, just the marsh level with some missions that they showed for the demo. Hopefully it actually gets finished on time.

Some Screenshots:



