I like the vertical buttons! I think they fit very well.
Agree.
For that particular window in that particular application, the question (for me) is: when do i actually click on any of those widgets and why? The answer (for me) is: i —almost always (over 67% of the time anyway) —click on the green goober to zoom down the main library/browser window to view something it's covering... and then —almost always (maybe 57% of the time) —click the same green goober again to return to its zoomed out state.
The way it has been (since iTunes 1.0) is that the mini-window state of the browser had vertical widgets and the fully-open state had horizontal widgets. That made quick zoom-down/zoom-back transitions quite awkward... because the green widget would jump away from the mouse pointer, when zooming in/out (unless we arranged for the proper offset by staggering the two views).
At least now in iTunes 10 we can arrange both zoom-states to line up properly and look smart at the same time (with both having vertical widgets), and thus easily collapse/expand the library/browser window without moving the mouse as much.
I do miss the little bit of color in the sidebar, however.
The best quip on iTunes 10 that i've seen so far:
The new icon sucked all the color out of itunes.
<edit> BTW, here's a neat page to compare the UI differences:
iTunes 9 versus 10[after the page loads, use mouse-pointer rollover to get the iTunes 10 version.]
