A great system with a novel level of presentation, but for the serious mountain bikeneer i can see the exposed belt drive and centrifugal weights getting caught in general trail leaf material.
A conventional rear derailleur is bad enough but a spinning o-ring style belt could prove to be the systems weak link, though that issue is easily fixed by enclosing the mechanical componentry.
As a town bike, it would "look" far more impressive if the components were highlighted with a colourful paint job to focus the eye on the moving parts.