Comment 18 for bug 912682

Thinking of what @CassidyJames said and from pure design point of view I don't consider transparent titlebars to be a good idea, because they break the consistency with the window bellow them *BIG* time (Win 7, anyone). That means even if this ... well whatever it is becomes a feature (gets fixed to look nice with all themes, buttons should stay opaque etc...) it should not come enabled out of the box.
Also, if "panel transparency" also affects the thumbs of the overlay scrollbars, that's gotta be a bug.