I wonder, it it was made from lightweight materials, what it would come to in weight.

Problems it solves: Infinite number of gears, being able to select the exact cadence you want at any speed. The gear range is wide enough; with a 305% on my Raleigh Twenty during my recent loaded tour I could ride almost everywhere, with 350% I can get everywhere.

I have not found any numbers for efficiency on Fallbrooks' site, but if it is 97%, everything else being the same, then it easily equals or beats a typical derailer system.

But I think they would need to reduce weight if it is to find widespread appeal in the bike market. Plus they need to cross the hurdle of the current paradigm that dismisses everything that is NOT a derailer system, as well as the historical attempts at CVTs for bicycles that turned out very inefficient, because as soon as people hear CVT, they say 'been there, doesn't work' just like for shaft drives.