I didn't notice any HDR, I don't think they recompiled it in. The map file sizes look to be unchanged as well.
I think the effects and all around shaders look a bit better than they did but its nothing to drastic. In certain places I defiantly feel a little more ambiance like the lab. Most noticeable changes for me would have to be the flashlight and 75o FOV to the 90o FOV. I knew you could change this in console, but its nice to have 90 as an option now. It feels much much less claustrophobic and open while playing.
One downside of this is that the title screens are now missing this new found 15 degrees of view which causes parts on either side of the screen to be showing where the map has been cut off, seen below. The displacements don't reach to the edge of the screen and the train teleport's into your view.

Lab looks way hawter. I think its the wider FOV that does it though.




