The left pane
I think the section Amarok#The left pane is a little bit confusing. It refers to tabs, but normally in our applications tabs refer to the little labeled bits on the top line of a pane (or sometimes at another edge). The "tabs" in the left pane reminds me more of an expandable tree view. I guess this is mainly a matter of appearances, but I still think it would be a good idea if we could come up with another phrase to describe "tabs".
Also when the tabs are referred to as retractable I think of something like the vertical file list tab i Kate, where the whole pane occupied by the tab can be made to go away by clicking the tab.