Based on a quick glance through the boards, I don't see anything, so ... Let's discuss it here!
I was suspecting the challenge would happen. I've been primal about 1.5 years (a little more now, I guess). Periodically, even without Mark's challenges, I do a month with no extra sugar and no grains. Otherwise, I just avoid them, but still eat out occasionally, or at friends' houses and drink or whatever. The only thing I completely avoid is gluten.
So, I started my own, personal, 30-day challenge on August 30th. I'm very gung-ho about this challenge, though. I love the things he has us do: the picnics, the recipe-making. Last year was my first time, and I'm totally excited!