Perhaps a little too much geometry considering the detail, the jaw line looks off. Lengthen the neck to allow the mandible to level out. Also maybe define the Zygomatic arch a little more, flesh will tend to hang off it rather than pudge out in this base expression.
Apart from that check out what the face is doing in that kind of an expression, you have modelled in the rising of the cheeks from the maxilla which only usually appers when peole smile or in old people, also the dippin in the cheeks happens when people are really skinny or open their mouth wide. If your modelling in neutral make it just that. Check out human anatomy books just to check yourself as you go.
The neck definitely needs a look, define the flow the of trapizius, sternocleidomastoid and clavical as well to help give the viewer an idea of this guys build.
I know that sounds like alot of crit but honestly its a good mode, the mesh is clean and easy to work by the looks of it, i really really like the eye region.
I hope this helps a little?