I discovered that you can now right-click (or control-click) in the title bar of an application to get the Customize Toolbar contextual menu. This especially comes in handy while using programs like Safari, where you cannot Command-Option-Click the Hide Toolbar button (because there isn't one) to achieve the same effect.

Tiger had the ability to right-click in the tool bar, but now it works in the title bar as well. This makes a difference when your toolbar doesn't have the convenience of a large empty space to in which to right-click in (i.e. Safari).