I have some suggestions,
first, the player controls area space compared to the right one of the search bar (see my previous post)
second, in the tree view, the selected font color is white in iTunes while you set it to black, which does not make a contrast..
third, the searchbar is not identical to iTunes (in iTunes the edit box is grayed and have a magnifiying icon to its left - all this are possible to make by the way)
fourth, I see that it would be better if you resized the playbar info box to the smaller size (which is in iTunes) and get the volume bar right to the playbar controls (right as in iTunes) and use small black graphics for (shuffle, repeat...etc) in the playbar info box (which i think would be better), note: if you wanna make this you have also to change the media mode buttons to lets say the right of search bar to make contrast with the left side,.. anyway if you don't have breath for the whole issues in this step ignore it anyway
if you needed any hand, pm me i would be glad..