http://www.wired.com/wired/archive/13.04/hybrid.html?pg=3
it's damn hard to develop an algorithm that manages a hybrid power train. No company has been able to come up with a formula that beats Toyota's.

Mercedes was stunned to discover that its vaunted F 500 Mind concept car, a diesel-electric hybrid, actually got worse mileage on the highway than a gas-only version.

[GM] convinced King County, Washington, that its GM Allison New Flyer buses could increase fuel efficiency up to 40 percent over conventional diesels. The county purchased 235 buses at $645,000 each, a $200,000 premium per vehicle over their existing fleet, only to realize that the New Flyers don't get better mileage.

Nissan just threw up its arms and licensed nearly all of Toyota's hybrid technology.