It is similar to a timing belt and it's supposed to last a long time with very little maintenance.
And it's quieter.
For me, coming from a 20-year old mountain bike with low-level components, it was an unbelievably smooth drive-train upgrade. With the NuVinci 330 CVT hub, it's also convenient and nearly idiot-proof.
But then I test rode a 1985 Guerciotti w/ Campy components and now I also want an old-school steel touring rig w/ some quality components.