I have to agree with rocketsauce, whilst I like the fact that the search bar now autosizes, I dislike it completing with playing now info... not only can it block text, but also looks visually inconsistent to me (having the playing now info constently resizing).
I'm not sure where it -can- go, but as for size - if it's going to be locked in size, it should be at least 3-4 variables wide if not more... however I love the placement of it over the panes (eg phelt's mockup), since this makes full use of window width & -seems- (with my limited knowledge) a more logical position for it (and doesn't really compete with anything else.)
I also agree that the 'Media Mode' buttons should be placed over the tree, I think this would make the changes more obvious to beginning users. Oh, and having the play buttons on the left too... so basically phelt's mockup of Quisp's mockup :) (basically I very rarely venture over the far right of the screen, so I only want rarely used functions over there, eg maxamise, min, close, dsp, filters, etc... not the play buttons... nor the search bar).