Would really like option-click on a disclosure arrow in the tree view to recursively expand/collapse subtrees. That is, when you option-click a folder open, it should recursively open all subfolders down to the leaves. When you option-click it closed, it should recursively close them all.
Other directory-tree UIs do this, including Sublime Text, TextMate, and the Mac OS finder, and I find it quite useful. Thanks!