The 8200i recently released in the US market (but has been available elsewhere for some time now) I understand has under-the-hood technical improvements over the 7600i...
A representative from Plustek posted on DPReview:
Hi Mark from Plustek here. A couple things....
The OpticFIlm 8xxx series scanners are the same hardware as the OpticFilm 74/7600 scanners. The only difference is SilverFast 8 comes in the box with the 8xxx scanners and you have to download it (free) for the 74/7600 scanners.
http://forums.dpreview.com/forums/read.asp?forum=1002&message=41824865
(Also note what he said about how they compare the upcoming Plustek OpticFilm 120 scanner with drum scanners.)
I am working through my family's negative and slide archives and what I am interested in are solutions that are cost effective and exist as products that are on the market. I'm trying to make a workflow that I can share with other members of my extended family and anything that involves chasing down equipment that can't be bought brand new is a non-starter. I really appreciated your review of the 7600i. I've been very happy with mine. (For the price.)
But I am still interested in camera scanning, because I think (but can't prove) that my 60D RAW files are giving me better color than what my 7600i yields. (I know that looking at 60D conversions at 100% often makes feel happy about the tonality, but looking at 7600i conversions at the same magnification makes me sigh. Generally.) And camera scanning is a whole lot faster than my 7600i is. But there isn't much to choose from for mounting slides and negatives in front of a camera/macro lens. That is currently in production. I've had good luck with the PhotoSolve Extend-a-slide with slides, but the ergonomics aren't optimal, And I haven't found the Photosolve negative carrier to be workable for 35mm. (I was able to modify the 35mm negative carrier to work for 110 negatives though. 110 negatives are problematic with conventional scanners. I am very happy that I was able to rescue family heirloom images from the 1970s and 80s that otherwise only existed as overexposed prints.)
And I am still going with Peter Krough's contention that camera scanning,
when implemented optimally, yields better results than can be achieved with Nikon (or Imacon) scanners. It is the "when implemented optimally" part that is tricky.
Back to Kodachrome.
Here is a link to an interesting discussion on how Kodachrome was processed, and how this affects the blue cast we get when scanning. The posts by Alan Marcus, the former Quality Control Manager at Dyancolor's Aurora, Illinois are especially interesting. He was trained by Kodak on how to process Kodachrome.