Changing over from a grid based system to a hex-based system would mean of course that gems wouldn't fall when those beneath them were removed, so the play field has been moved into zero gravity. Now, the gems will "fall" in the direction that they were swapped. Move a gem diagonally up and to the right and the gems from diagonally down and to the left will move to fill the space.
If that sounds confusing check the gameplay video after the break. And the current release window is the first quarter of 2009.