I have been testing pixel shift vs single capture for a few weeks now on a Panasonic Lumix S1R. Before that, I read about it constantly for a few months off and on trying to understand the value - perceived vs real.
I have not had the opportunity to test FF pixel shift vs digital medium formats 44x33mm (Hasselblad/Fuji’s “affordable” MF) or 54x40.5mm (Phase One). They surely do amazing things with single image, 16bit capture. And some of them have pixel shift abilities as well.
I am sure you Nikon will do a stellar job of the task!
I also have gotten to test pixel shift vs dedicated film scanners of various kinds. I am quite happy with all the results of both single capture and pixel shift vs different scanner types. To each their own but camera scanning is where it’s at for me - raw files and post-capture edits rule the day.
My version does 8-images to produce a raw file in-camera. This unusual feature is why I chose the S1R, rather than adding a step with external combination software on other cameras. A used S1R was also more affordable than the other options by a lot. As I have talked about previously, I am working on digitizing a huge archive from a single photographer, in total over 350-400,000 35mm images.
What anyone else chooses to use is personal though so not wanting to debate that. They all do the same thing roughly as long as it is 8/16 images. The 4 image combo type is just for recording full RGB (which is also useful IMO).
TLDR of the longer thoughts below: Pixel shift has great benefits if you can utilize them. But the film emulsion cannot give what it does not have as far as detail goes… so for viewing on nearly any screen and for prints smaller than, say, 16-20" on the long edge I think there is limited usefulness of the technology. At some point, you just “scan” deeper into the grain or dye clouds. Also, alignment and vibration becomes a huge issue compared to single capture.
For me, its the perfect and affordable tool to make higher quality scans of selected images for public presentation and long term preservation. The effort it took to get here was considerably harder than I expected and I am not done trying to perfect it.
For most people I don’t know that pixel shift has strong benefits unless they are printing physical books, cropping extensively, producing large exhibitions or involved in scientific and cultural heritage applications or library and historical archives purposes.
Also, I think the evidence is clear that museums, libraries and archives the world over have nearly all switched entirely to camera capture techniques and this is the way of the future. As far as I can tell, few to none of them use pixel shift techniques but they are often using 150MP 16bit Phase One specialty cameras and lenses. And they are often taking more than one image of the object/films at various distances for preservation purposes. Take from that what you will. This is typical but not always the rule, these places work within the budgets given to them.
“Briefly” on various topics
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Sharpness: the images are not sharper, per se, in the grand scheme at real viewing sizes and distances. They are as sharp as the original film and lens made them. However, there is more data captured at the grain level and it has much smoother, finer transitions within colors and edges when you go in to 400% or more. A win, IMHO, but not for the reasons most would expect. The images at extreme magnifications appear to be softer. While at normal viewing distances only a little better or not at all. But in the lower resolution single capture images it is simply the effect of hitting the pixel level of the image, creating artificially sharp edges once zoomed in far enough. I find the grain more pleasing in the high res pixel shift images because it’s smoother, more like it would be in a print because light and enlargers dont use pixels. Said another way, more and smaller pixels means those edges have more detail and thus cleaner transitions at typical and 100-200% viewing distances compared to the lower res image. Great for a 60inch wide print or a 50% crop, but of limited or no utility at all for an 8x10inch print or Instagram.
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Resolution: related to more pixels mentioned already… a clear win on the condition that you want to print it large at 300dpi and/or, especially, crop extensively. Otherwise you just have huge files. Final viewing size and viewing distance is what matters. So subjectively useful depending on your needs.
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File size: a clear challenge for this technology. The files get very large. DNG conversion and compression can help theoretically though I need to test what downstream effects that has on the images, if any. But quite frankly at large sizes a final TIFF image is often similar. I ONLY do pixel shift on selected and important images for preservation and exhibition, otherwise the size penalty is too great and the process too slow for the volume of images I need to get through.
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Full RGB capture: a huge benefit for printing IMHO - cancels out the Bayer pattern interpolation that must take place for the algorithms to create all the colors. For accuracy sake, I love this, especially for slides that can have huge contrast and density compared to negative film. There is some thought that the more accurate RGB color data should provide better color bit depth and dynamic range. That all said, do we fully trust Bayer-pattern interpolation of the colors? Many would argue yes! Including many of the archives I mentioned up top. I do wonder how 14bit capture of FF pixel shift compares to 16bit MF single capture. The one comparison I saw, using math and theory not examples, was compelling and showed that 14bit pixel shift was similar to 16 bit single capture.
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Post-Production: all of this combines for a more creatively capable file. Sharpening in post is much nicer and controlled. And color correction or modifications for printing is, again in my opinion, more flexible at this point due to real RGB. I will always take more flexibility when working on creative projects.
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Alignment: much more challenging than single capture. Honestly sometimes a pain. Alignment can look good at 24/45 megapixels and bad at my pixel shift 187 megapixels. Being truly meticulous and checking occasionally while you work is essential. The mirror “trick” is fine for the ball park but I find if I want it to be perfect, I must get more specific and do some testing. Focus peaking works about the same using test targets. Seems easiest to use B&W film grain in the 4 corners and center to check yourself after centering with a mirror or peaking on a test target.
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Vibration: I am on the upper floor of an older house and if someone is walking elsewhere in the house I can see it on the live view and in images after capture. I have put cork pads under the table feet and anti-vibration pads under my stand. Doesn’t stop it but they subside/settle as soon as the movement stops now.
That wraps up my Ted-NLP talk on pixel shift. 
Thanks! Still hard to believe that it’s possible to scan 300 000 in one’s lifetime