This lens is a reason for someone to make the transition to FF.

It is the widest rectilinear FF zoom lens regardless of the manufacturer, and the images it produces at 10mm are simply impressive...
It is not the sharpest lens and it has noticeable vignetting, but it compensates with the overall result.
It is sharp in the center even when wide open, but the edges require 1-2 stops down for the best/uniform result. Every photo feels like a panorama!
Very high-quality construction and quite small for what it is. It balances very well on the a7R II.
It is so wide that even on a crop body, it remains wide-angle!
The best focal length is between 10~14mm.
It accepts 37mm filters (!!!) on the back or 100mm square filters with the dedicated filter holder from Laowa.