Article on the XX1 drivers.
I found this comment helpful:
"XX1forOldSingleSpeeders - 12/27/12 - 10:25am
XX1 is an excuse for old and worn out single speeders to switch to gears without compromising their desire for simplicity. Those same MTBAARP folks will probably pick up a full suspension ride to go along with it as well."
Woohoo my new Mavic Crossmax's will get the new driver