The Cielo X1 2.0 is Hoka's marathon racer. Two layers of PEBA foam sit under a winged carbon plate, and the forefoot rocker is steep enough that the shoe wants to tip forward on its own.
It is a race-day shoe and it earns its place there. Running a half or a marathon flat out, you get energy back from the foam that a trainer will not give you, and the plate keeps your foot from folding when your calves stop cooperating late on.
It is not something to train in. The foam is expensive, it compresses with use, and every easy mile you put through it is a mile you do not have on the day. It also takes acclimatising to, so run a few sessions in it before you pin a number on.