Aboudd, I've come to some different conclusions. I've used both the Nikkor and Schneider PC lenses (28 and 24mm). The Nikkor went back to the rental house and I bought the Schneider. There may be sample variation involved, and there are definitely a lot of variables to deal with in a shift lens ... more than in ordinary lenses. I found that the weaknesses of the Schneider were worse than those of the Nikkor, but that its strengths were dramatically more impressive ... and with the work I do, I can avoid the weaknesses.
The Schneider is the sharpest lens I've used on a small format camera—unshifted. The performance declines toward unuseability at maximum shift, but at the halfway point it's respectable enough that I'm happy. Its ideal aperture range also changes significantly with shifting. It takes some work to get the best out of this lens. The Nikkor was a bit more consistent over a wide range of shifts, but its performance was no more than very good in any area. I found it highly competent, but for that kind of money I want to be excited.
I'm very interested in the new Schneider, because unlike some of their lenses (my 28 PC and the newer 50 PC) it does not appear to be an older, recycled optical design. When Schneider does its best work, I believe they outdo any other lens company (not counting Rodenstock, who seems to be their equal).
Unless Schneider really pooped the bed with this new lens, I would expect it to outperform my 28 and anything by Nikon or Canon. And probably also Zeiss. I've played the internet parlor game of Zeiss vs. Schneider many times over on Rollei websites, and the boys of Kreutznach won my vote about 9 times out of 10. And this was mostly with pre-digitar technology.
I do most of my work in fairly low light and don't think f4.5 is an issue at all. I will gladly trade a big maximum aperture for performance at the apertures I actually use.