Very interesting, Kris! You have a pretty good eye for anatomy profile anatomy. ;o
As for the critiques:
1. The neck seems rather awkward, like.. it's too towards the back or too long. I'm not sure if this is just the angle that the picture's taken at though.
2. The top of her head, hair, and down to the nape of her neck looks a bit off. I think it's just the lack of definition though -- it makes her skull look small compared to her face.
Putting those two together, I think I'm seeing too much space from the outter corner of her eye to the ear, making her face seem larger than the rest of her skull should define her as.
As for colouring hair, find your light source and pick put the darks and lights. Block in the darkest parts and the "inbetween"areas to the appropriate scale. And then pick out some of your individual strands and detail them in with quick strokes or erasures with one of those pen-erasers. For the area that the light hits, just add in some light strands to give it definition. That way you give the illusion of hair without doing every strand (which is impossible and generally makes it look more fake than real.)
You did a pretty good job on the face -- and I know you're an artist so all you really need to do is to determine your light source and figure out where to go from there.