According to FoneJone at a Google Blogoscoped thread, Jacob Millston of Georgetown, VA won the Da Vinci Code quest. I’ve been unable to find any other sources for this, but I don’t see why FoneJone would have have any incentive to mislead anyone.
Looking back on the final challenge, I really wish Google would have made the puzzle generation random. Oh well. Congratulations to the winner, and better luck to everybody next time Google decides to put on an Internet quest!