The Ultrafly is a super-shoe for the mountains. ZoomX foam and a full-length carbon plate sit over a Vibram Megagrip outsole, so you get the propulsion of a road racer with grip that holds on wet rock, and an upper built to drain when the day is wet. It is made for long trail races where you still want to move.
It is a lot of shoe to be running on uneven ground. The stack is tall and the plate is stiff, and on technical terrain that costs you ground feel and some control.
It is not a daily trail trainer. The foam does not last, so save it for the races and the biggest days.