The last time I updated the reconstruction, I was somewhat satisfied with it, but not completely. There's always something that's not quite right. Today I fixed the chin a bit and reduced the size of the eyelids so they look more natural. I also slimmed the nose just a tad and worked on the mouth. Now it really is much closer to what I imagine the original Sphinx looked like.
Have a look here if interested.
I read somewhere that the ancient Egyptians forbade artistic depictions of people in anything but glum, expressionless poses. That explains why the Sphinx appears stoned, with his very stoic expression.