This thread on 4OSX.com posts (real) screencaps from Panther. [ mirror ]
[Update: 4OSX.com has removed the images.]
Depicted in the screenshots are: Finder Window, Mail, System Preferences, Expos Panel and in action, DVD Player, iChat 2 with VideoConferencing, Activity Monitor, Labels and Finder.
Sherlock is reported to be at 3.6, Safari at v85 (1.0), X11 included, and additions to Address Book. The new Finder uses a Metal theme.
A new feature called Expos appears to be a yet-undescribed feature providing you with an overview of mini-versions of your windows, organized geographically by type of window.
Reports indicate that the rumored 'Piles' feature is nowhere to be found in the latest releases.