Not sure how I can judge the efficiency. I can say that I am slower, on both the Stoater and my traditional deraileur-geared bike, but I put that down to the fact that I'm coming back after a knee replacement and I'm a bit older than I was. I can also say that, purely subjectively, the Gates belt drive feels very smooth and it feels like the effort is being put to good use. This may be down to the stiffness of the frame. When I visited the workshop, Steven Shand explained to me that frames built for use with a Gates carbon belt drive need to be designed and built with a minimum of flex around the bottom bracket and through the chain stay, as the alignment of the belt is critical. I think I can confidently say that he has resolved that issue. Plus, the Stoater is a very comfortable bike to ride.
As for the Rohloff, I've used them before and, imho, you either love them for what they are despite the weight penalty, or you don't. I wasn't looking for speed when I commissioned this bike; I wanted something robust, and I think the combination of a Gates belt drive and a Rohloff transmission fits that bill.
Overall, the Stoater is a delight to ride, and the way that the frame has been designed to accommodate the equipment, and its superb build quality, puts a very happy smile on my face. (These pictures don't really do it justice, as the front pannier rack makes it look a mess.)
