I like the comparision of the belt drive and this clean sort of bikes for
using in urban terrain. It is great to have such a silent drive while you
are making some funny, speedy or athletic stuff.
But talking about efficiency or acceleration on a pro level, I would think
a chain drive would be better.
(Thats why the Heidelberg is displayed under the rafael concepts label and
not under rafael sports)
For real track racing I choose the normal chain drive. It works perfect,
and nobody worries about dirty legs or trousers. And you have more choises
in transmission ratios (for the moment - they will produce a lot of new
sizes, I think)
I have made my own special pulley attachment.