Great lens if you respect its limitations.

Near the axis, at mid to small apertures, this lens is sharper and better looking than my Nikon 14-24mm f2.8 zoom, which is a state-of-the-art optic by most standards.

As a shift lens, however, we're interested in how it looks off-axis. Sometimes way off-axis. And here things get complicated. Which is why if you scour the internet, you'll find reviews ranging from "best lens ever" to "worst lens ever." I don't know if there are quality control issues at play, but there are almost certainly issues of expectations.

If you're looking for a lens that will be sharp in the corners, at a wide aperture, at maximum shift, you won't find that here. You will instead find corners riddled by astigmatism (smeared detail), chromatic aberration, and distortion. I don't think there's any shift (or large format) lens that will perform brilliantly in the corners at maximum displacement. Certainly not at wide apertures. Canon's 24mm t/s lens comes pretty close. I haven't had a chance to look at the astronomically priced new Schneider 28mm (which I expect to be good but not miraculous, based on the medium format lens on which it's based).

In practice, I've found that the Schneider works best if you keep the shift within 6mm (like Nigel's amp, it goes to 11, but probably shouldn't). With any shift at all it looks best at f16—ot f11, not f22. It's really a very narrow window. I'll make exceptions and shift more if the upper corners contain sky or something else lacking detail. And unshifted it looks fine at wider apertures.

If this sounds like a serious set of limitations, it is. But I find it more than acceptable for the industrial landscapes  I've been doing, which require a ton of depth of field. I'd have to stop down anyhow. And 6mm of shift has proved to be more than adequate most of the time.

Working with a Nikon d800 mounted on a heavy wood tripod (borrowed from my 4x5 camera), focussing in live view and shooting with the mirror locked, I've made many images that look stunning at 40x60 inches with this lens. My printmaker says they look like prints from 8x10 to his eyes. I don't know about that, but they look a lot better than my 4x5 darkroom prints at similar sizes.

They don't look perfect. The upper corners (when shifted) are softer than I'd like, and often a bit smeared from astigmatism. Chromatic aberration takes a lot more work to correct with a shift lens, because it's asymmetrical (the software expects your lens axis to be centered in the image). But I find that I'm the only one squinting into the upper corners. The overall effect of these prints is brilliant.

I've rented the Nikon 24mm shift and don't like it as much. It's a little sharper off axis, a little softer on axis, so optically the differences aren't huge. Mechanically, the Nikon is crappier, and it's more expensive (for some reason, you can get some bargains on the used Schneider). This Schneider doesn't tilt. This could be a deal breaker for some, although I don't find tilt useful at this focal length for how I use the lens. I'd love to use the new Schneider t/s, but at street prices north of $8000, forget it. So currently, I think this aging shift lens is the best choice, at least if your needs fall within it's fairly narrow window of strengths.