I just don’t get this design. At all. The eye is distracted by the drop shadows, which lift the sidebar and buttons ‘above’ the content (ie the icons) and the title of the window. From a visual hierarchy standpoint, it makes no sense.
The menu bar also just feels weird without a background. I suppose we should count ourselves lucky Apple hasn’t forced the iPad version on us, because that’s even worse. (And, yes, I know you can – for now – bring the background back.)