There are various opinions about this lens. I supose this variety of opinions depens on sample variation. I tried two samples, one from a friend just to test it and the copy I purchased based in my good impressions when I tryed my friend's copy.
My copy is very good, almost impresive at the default position at 11-8 on an 1ds2. Shifted to a maximum of 7mm maintains the very good performance and from 8mm decreases gradually, but this quality decreasing is not dramatic, and if no detailed subjets in the corners, no one can notice it. If corner detail is needed at maximum shift use 11.
Distortions are just noticeable and easily correctable in PS, and CA's can be easily eliminated. All in all a very nice lens when tilt movements are needed.For general purposes 1,4/24 or 2'8/24-70 are better options.

This lens gets a bad rap from a lot of people which I feel isn't fair. It is a unique lens in the photographic world and allows a world of creative exploration impossible without a view camera and a Super Angulon or similar lens.

Build quality is superb. The solid, thick metal body is nicely sized and all locks, knobs, and etc. operate smoothly. Focus is buttery smooth and properly damped as this is a first rate manual focus lens.

Wide open and unadjusted it is quite decent in the center, with sharpness tapering off a bit towards the edges. Stopped down to f/5.6 it has already improved with nice sharpness across the entire frame. By f/8 the lens is stunning across the entire frame.

At maximum shift, the lens still performs admirably. Wide open, edge sharpness (toward the shifted side, away from the center of the projected image) is adversely affected to some degree (of course) and there is some CA present that was absent when the lens was unadjusted. The image is darker as well. By f/8 the lens has improved to some degree at the edge of the frame, but sharpness isn't at the level it is when unadjusted.

Tilting the lens seems to affect quality less than shifting, assuming one is aware of the Scheimpflug principle and can find a subject that is also properly tilted. Quality is still diminished slightly compared to the lens unadjusted, but this is of course completely expected and doesn't reduce its utility.

This lens gets a bad rap from a lot of people which I feel isn't fair. It is a unique lens in the photographic world and allows a world of creative exploration impossible without a view camera and a Super Angulon or similar lens.

Build quality is superb. The solid, thick metal body is nicely sized and all locks, knobs, and etc. operate smoothly. Focus is buttery smooth and properly damped as this is a first rate manual focus lens.

Wide open and unadjusted it is quite decent in the center, with sharpness tapering off a bit towards the edges. Stopped down to f/5.6 it has already improved with nice sharpness across the entire frame. By f/8 the lens is stunning across the entire frame.

At maximum shift, the lens still performs admirably. Wide open, edge sharpness (toward the shifted side, away from the center of the projected image) is adversely affected to some degree (of course) and there is some CA present that was absent when the lens was unadjusted. The image is darker as well. By f/8 the lens has improved to some degree at the edge of the frame, but sharpness isn't at the level it is when unadjusted.

Tilting the lens seems to affect quality less than shifting, assuming one is aware of the Scheimpflug principle and can find a subject that is also properly tilted. Quality is still diminished slightly compared to the lens unadjusted, but this is of course completely expected and doesn't reduce its utility.