A lower-resolution YouTube demo from Lynda.com is available here, if you don't want to download a huge QuickTime movie. The content is different, but you'll get the idea.
Adobe licensed an algorithm that senses "dead" areas in photos, and resizes the image to avoid squashing or stretching every object.
In the video, Brown demonstrates resizing an image of four golfers, interactively removing space between and around the golfers, but leaving the golfers' proportions correct. He also demonstrates resizing a Volkswagen bus, making it a more "economical" size, but automatically keeping the wheels round.
For those looking for a compelling reason to upgrade to Photoshop CS4, this might be it. If not, what is? Let us know by leaving a comment.