The boys have been spending a lot of time working with the bead chains and following up the work with the game SPEED! I posted about SPEED! when we bought the game back in May. We haven't indulged yet, but the game SPEED is now available as an iPad app.
Me Too has been heavily interested in any chain except 9, 8, and 7. Conversely, Kal-El has only been interested in chains 9, 8, and 7.