Keynote slide transition: how do I....

[Pittsax]

...get my slides to transition where some of the letters on the previous slide shuffle to become part of the next slide? Steve's latest keynote speech had this animation, and I first really noticed it in the end credits for An Inconvenient Truth.

I know I could do it by animating paths for individual letters, but I'd hate to think how long that would take. Is there a way to do this yet, or might it be a feature in the latest version?