Not one of the best Zeiss lenses, but a solid performer anyway.
His strongest point is the colour rendition, tipically Zeiss.
100% crops. Left center, right borders (on Canon 5D Mark II):
On the other side, resolution wise, it is not better that a Canon 24mm f/2,8, especially at the borders.
Good if you have other Zeiss optics, just for colour consistency, or if you prefer to focus manually.