Personally I think its pretty good overall on that head however, its a little crowded in areas with loops etc that can be sorted quite easily.

I think the jaw is okay, Ive seen worse on here. Even with the flow you have now its correctable and very useable, I just think the cheek area below the eye and also the loops around the mouth are in need of love.

Ive drawn over the original with my new red pen, which is now green

less polys to work with and better control, Ive also hinted at the brow area in terms of poly shape etc...

hope it helps
Jay