Speaking with aforementioned Mac-OS-X-reviewing friend, I'm puzzled over just what the Cocoa drawer widget is for. In the Quicktime player for Windows, it held media service icons like the scrolly bit in the left of the normal RealPlayer view. I figured it was something for dialogs with 'Advanced' options that double the size of the dialog, as that's what the Messages screenshot for JabberFoX seems to imply--but no, the Group Chat shot uses it at the side for the group roster, and OmniWeb (I think) uses it to display bookmarks. Apple has nothing to say about it yet, but hopefully they'll have time to shed some light.
Does anyone know?