My score is 714 and myfico says I'm higher than 49% of Americans. That would mean the MEDIAN score is probably around 720-730ish. Due to the fact that it can only go up another 100 points, but there is a broad spectrum of lower scores, I would expect the average to be below the median... So probably mid 600s.
Everything I said above, however, is completely worthless information compared to actual numbers these guys have receieved from myfico, etc.