the light source looks off to me. the top window frame looks great, but the user pane and status bar pane have 2 light sources one on top and one from the bottom. the start button looks awesome but here again the task bar background has 2 light sources and screws it all up..
in each of these areas the light is also too strong and washes out the color resulting in an inconsistent look.Also add some awesome original buttons, the start button is killer maybe different variations of it would be good...
I will say it has potential and I love the concept. keep up the good work. I hope my comments helped

HG_Eliminator
Leader of the dark skin following, SK mentioned.