your highlights look really well rendered! It feels like they give a hint of the pores and the lush texture of skin, instead of looking all dried out and pasty like mine.
I am trying to figure out what is wrong with the lips though, they're bugging me. Like the bottom lip indents towards the mass shadow or something... some of the shadows in there make it appear too concave?
In my first render I also didn't really bother to finish the neck or shoulder, but I think JM's advice really helped strengthen the overall piece, to render and soften the neck and shoulders a little more.
I used a hard round brush, and I thought it was going to look really bad and soft I usually use a brush with a little texture, trying to get something like traditional ahah
Here I did (tried actually) what you said, the lips is buggin me too, but I dont know if that was the solution.
also a good start...the modeling in the light is looking solid. The modeling in the shadows...i.e. the info in the shadows that suggests a bit of form detail or expression seems to be missing. Check your eye to see if you can see pupil. Just that detail may spark the life into the piece more. Keep it up!!