Can you speak on the "Battledecks?"

Here's a speaking competition for the courageous: Battledecks, a competition in which you have to extemporize a coherent presentation while you see slides chosen for you for the first time--and they don't always seem to go together.  Of course, it's also timed, with judges, an audience, and no doubt, a lot of laugh moments.  Some call it "PowerPoint Karaoke," but I'm not sure that's apt (after all, in karaoke, you already know the song).  I've asked some folks who are participating or have participated in Battledecks to share their experiences in guest posts; there's one coming up at the American Library Association meeting, but Battledecks can happen at any gathering.  Have you tried this?  Tell us what it was like...