Actually it's old technology. Supposedly this technology existed before the chain drive, and this is what Henry Ford used when developing ... well, whatever he developed that had to do with this stuff!

Most people will tell you that it's less efficient; of course the website says it's more. I dunno. My husband had his heart set on them (less maintenance and geeky cool) and that's what we got! We haven't any other bikes to compare them to.