I've done it twice, and will be doing so again in May. I love it. It's a huge rush. And if you participate in a good one, like the one they have here in Dallas, they get Red Bull to be a sponsor and have a truck driving all over the city delivering free caffeine to the participants. It rules.
My friends and I always try to up the ante; our first year we made an epic musical, and last year we made a 70s style action movie about a Masonic private eye pursuing an evil Mexican Wrestler. You always have certain themes and props you have to work in, so that makes it even more crazy.