The most efficient drivetrain
The drivetrain efficiency on a modern bicycle peaks at 98% in optimal conditions and down to 93% at realistic power outputs. Efficiency varies whether it is in high gear (higher efficiency) or in low gear (lower effieciency).
CeramicSpeed's Driven chainless drivetrain claims to have a 99% efficiency in optimal conditions and creates 49% less friction than market leaders.
Driven's pinion drive shaft design is said to eliminate most of the friction caused by a chain and derailleur system.
Without the chain and derailleur, CeramicSpeed improved the aerodynamics of Specialized's Venge by approximately 3% consistently.
No Rear Derailleur
Other than the efficiency gains claimed, a mountain bike without a rear derailleur means that you won't be risking a broken derailleur as a result of interactions with the terrain.
Also, since the drivetrain will be covered, it is protected from sticks, mud, and sand, which could cause shifting problems.
Not of the present
There are currently two versions of Driven by CeramicSpeed: a shiftable version and a rideable version.
The 2018 version of Driven is only single speed and could not be ridden.
Now in 2019, they've made a version of the drivetrain that could shift for Eurobike 2019. However, the shiftable version is still not rideable.
A rideable version of Driven is only available at single speed and could not handle the full torque of a rider. So the rideable version may not be actually rideable.
If CeramicSpeed could pull it off, Driven may be the drivetrain of the future.
But that's not likely to be anytime soon and they could fail due to lack of funding for research and development.
"3% Faster" claim busted and more
A bike drivetrain that's highly efficient is nice but this attempt by CeramicSpeed doesn't actually work in real life yet. It's still in the concept stages and seems likely to fail. But if Driven does suceed, it's probably going to be the standard in bike drivetrains.