Looking good! I think you did a real nice job around the mouth especially. The main problem I see is some star trek stuff going on where the nose meets the brow. It is much too thick in yours. Also, the brdige of your nose is pretty straight, in this it is highly curved. I made some edits on these topics, plus a few other things too.

Also, remember that the tips of the mouth, in a normal person, align vertically with the middle of the iris. I widened the mouth a bit to account for this, but it could probably stand to be a bit wider. One thing I didn't do, that I think you should, is enlarge the eyes a bit.
Keep up the good work!