I think the usability of the new expand and collapse icons could be improved: when I first spot the new expand and collapse icons, I tried to click on the + button to expand the portlets. It took me a while to note that I first need to collapse a portlet before I can expand it. Maybe you should rather show only the available actions. Otherwise a (new) user expects that expanding a half-size portlet will expand to full size.
(Maybe using the minimize, restore, and maximize window icons will also improve the usability, but I'm not sure...)