Having finished the game I encountered a few bugs and figured it can't hurt to make a thread and let you know. First of, really great game, can't wait for the next 5 :D
There is a tiny "bug" with the psychiatrist sybill, the texture of that form is rotated 180 degrees so shes making her marks on the wrong side of the sheet.
I know I know very tiny thing, but it struck my eye.
A more serious thing I encountered was in the second dream sequence. Starting from there I had problems using the inventory. The mouse pointer didn't change back to the standard pointer after I used something, and when I did use the gun, Sam put it away again after using it, but the animation still had him sticking his arm out like he was still holding it. Looked kinda bizarr but was just odd and didn't affect your ability to complete the game.
Great work guys :D Oh and I think the difficulty is just right and the voices are spot on imho. So two thumbs up :D