I'll add that it's not a Nikon or Canon, the workflow and handling come with practice. However if the highest quality images are your goal, nothing short a MFDB will get you the quality of the Kodak's, period. It is an unforgiving beast at times, until you sort out issues like the lens optimization adjustment for each lens, you are using Photodesk, aren't you? If not download it from Kodak's website before it disappears, you may find all your issues suddenly go away. I do know that as good as ACR is on my other camera's, Photodesk is really needed for the Kodak's to get the best image from them.
<edit...> Thinking about this, there's two issues from what I can see, one is a focus/paralellism issue, though it would affect an entire side, not just a corner. The most likely culprit is the demands a non AA filtered sensor make on a lens. Do you have a fixed focal length, high quality lens available in the 50mm range?
I would first establish that the focus screen is consistent with the imaging chip, then verify (at all apertures from wide open to fully closed) that it's not a imager issue. Were the sensor failing, it wouldn't show up as softness, I'm pretty sure. I ran into a similar problem with my Hassy, when I first got a DB for it, nothing seemed sharp, it wasn't until I refined my focusing technique and started to get really attentive to details did the back really start to shine.
The second issue, and one that you haven't answered yet, is what raw processing are you using? the EXIF data is stripped so I can't tell, but using anything but Photodesk will cause you no end to grief with white balance issues, as well as color, sharpness and lack of DR issues. It really is that much better.