overal shape of skin is basic and quite good I think. But you could use some shadows to blend the outside stroke more into the fill. Progress bar could be done with same steps like you did volume bar which is the best part of the skin. I see you used 3 or 4 fonts in there and thats way too much. I advice you to get rid of handmade scripts and classical scripts in GUIs since mostly it just doesnt fit together because most of GUIs are dont in modern way. Ratings are done in creative way but they also doesnt fit to the other things. Stay in one theme and one style when making skin and next time it will look much much better. Good luck and I hope you take this critism as an advice and not as insult.