I'm a bit leery of a belt drive for two reasons. First, the break in the frame. Second, the potential issue with gravel. In the motorcycle world, belts + gravel = bad. On my bike I tend to ride through rougher offroad type stuff often...cutting through ditches, offroad trails etc.

I'd like to see how they respond when gravel gets in the belt. My fear is that it would jam the drivetrain, leading to a potential crash. I guess if you got a full "belt"-case to go around it this wouldn't be a problem.