Canon's 14mm f/2.8L ii is top-notch in the world of ultra-wide prime lenses. While it's not meant for portraiture or every day shooting, it is a specialty lens that excels in architectural, real estate, landscape, environmental and some street photography settings. I've been delighted with the lack of distortion, since most ultra wide angle lenses that I have tested take on a borderline fish-eye appearance. Note in the sample shots below the perfectly parallel lines, particularly at the margins of the image. Colors are accurate and well saturated. Since most architectural photography is shot at a smaller aperture for a broader depth of field, I experienced no chromatic aberrations--ghosting, flares and fringing were completely non-existent. When pixel-peeping, I was astonished that the clarity of the extremities of the images was nearly as sharp as the center. The crispness and lack of distortion that the 14/2.8Lii offers is far superior to any zoom that I have tried in the past.
The large, heavy construction screams quality, as I would expect in an L-series lens from Canon. The bulging, convex front lens element is marginally protected by a built in petal shaped lens hood. Consequently, traditional lens caps and filters cannot be used with this lens -- and great care is needed to assure that the glass is not damaged. While I wouldn't shoot in a downpour, it's a bonus that the 14Lii is weather sealed.
The 14/2.8Lii is insanely wide and not for everyone. This genre of ultra wide lenses (defined as a focal length shorter than 15mm) can be a challenge to use. Most people believe that ultra wide angle lenses are for "getting it all in", but images rendered can appear as a broad expanse with no compositional interest or clear subject. Force yourself to get closer to your subject when using an ultra-wide lens to push key elements to the center of the frame. Monitor the composition at the edges as much as the center of the image. And remember that these ultra wide angles lack the compression of their long cousins, so the difference between what is far and near is exaggerated. The 14/2.8Lii can create stunning architectural photos which make interiors appear more spacious, although you must take special care to keep the camera body level and at the critical height to ensure that all lines remain parallel. Alternatively, this specialty lens can be used to create some crazy angles and dramatic effects using every day items.