#1 the light is too hot, and the shadow side is noisy, like you cranked on the Fill Light slider.
#2 Is pretty cool, but I wish the hair wasn't in front of her right eye. Also, with shots like this, it's better to go to full profile, so that she doesn't have eyelashes growing out of her nose, but no eye to go with them.
#3 is really nice, butthe skin is a bit to plastic for me, and the weird shape of her shirt's neckline keeps drawing my eye away from her. Thehair light is a little too hot, and what is she doing with her left hand? Does she have an idea, and speck in her eye, a migraine? It doesn't help that he eyes are looking really far to the side.
#4 look pretty good, but it looks like you lost some detail with the shirt. Also, the image makes me ask myself,what is this white cube and why is she sitting on it?
All of the images could use a separate light on the background.