In the FAQ they compare the weight to a triple. When talking about the range, they suggest a low-high gear range of around 153%. My Shimano 105 5703 triple provides a range of 424% which I consider sufficient.
Even a Nexus 3 speed gives you 186% range and a close ratio 12-23 cassette gives you 192% when using only one front ring. Looking at the video how this front "chain ring" expands and contracts, I can't see how the range could be expand much either.
This design is basically gearing for people who don't really need gears.