Every motor scooter you see not more than about 5 years old has a CVT. It keeps the small engine used at a constant RPM so the engine is running at its most efficient RPM all the time. It also eliminated manual gear shifting so women purchase and ride them. They're also starting to show up in automobiles designed for maximum fuel economy. At this time a bicycle CVT costs considerably more than a derailleur system but this is about to change. The current patents on bicycle CVT systems are due to expire so everyone is waiting for that to happen. Hence, no investment in the company's that developed them. Watch the Chinese mass produce them and link them to the pedals with shaft drive eliminating the chain entirely. This will be good for comfort and MTB bikes but road bikes will continue to use a chain just like crotch rocket motorcycles. You will also see them retain a front derailleur and multiple chain rings on touring bicycles for mega range drive systems. The internal workings are pretty simple. Picture two cones or funnels placed side by side linked with rollers that move up and down between the angled surfaces. Moving the rollers up and down changes the ratio between input and output with a ratio of about 3 to 1. A considerable range of adjustment! The cones and rollers may be aluminum or if weight is a consideration and cost is no problem titanium may be used and the weight need be no more than the traditional hub, cassette, and chain. Index shifting and adjustments are a thing of the past. Simply rotating the shifter and pulling the rollers up and down the cones provides the infinite ratio changes. Just think of a friction shifter where you need never "find" the required cog. Here is a link to everything you ever wanted to know about the CVT.
http://www.gizmology.net/cvt.htm

Here is the continually updated commercial resource site for CVT systems.
http://cvt.com.sapo.pt/toc_en.htm