Hi, Eric,
Yes, I remember the debates. I certainly don't have the authoritative scoop on the difference between an AF vs an AFD lens, but I did speak with several folks from Sinar, Leaf and F&H in person, probing for specific answers. Here is what I have been told:
The AFD lenses (Super-Angulon 50mm f/2.8, Xenotar 80mm f/2.8 and Tele-Xenar 180mm f/2.8) are optically unchanged, have improved internal flocking, are manufactured to tighter mechanical tolerances, and are verified to deliver at least 60lp/mm, whereas previous lenses were verified to deliver at least 40lp/mm. (Sources: Sinar, F&H)
Additional observations:
* I don't recall clearly if the AFD Tele-Xenar 150mm f/4 is also unchanged optically, but I'm 95% sure it is also unchanged.
* What changes might have been made to the planned AFD
Makro-Planar oops, Apogon 120mm f/4 are completely unknown to me.
* The upcoming AFD Flektogon 35mm f/3.5 obviously has no predecessor to match.
* What is meant by "60lp/mm" (what part of the image circle, at what aperture, at what scale, what contrast) has never been specified, to me at least.
* No photographer I have ever asked who has seen both AF and AFD lens results (myself included) has ever said they could see a difference.
* I have never been told that the AFD's are better at bringing all colors into focus at the same plane
* I have never been told that the AFD's "compensate" for filter glass in front of digital sensors (whatever that means)
* I have never seen an AFD MTF.
* I have been told that the AFD's deliver "better image quality" by F&H and now recently by DHW, but specifics have not been provided.
* There is a clear difference with many of the AF and non-AF versions. A whole
set of Rollei manual and AF lens specifications were posted over on photo.net some time back (click "show details" to see which lens each graph represents)--these confirm optical formula differences between manual and AF versions of the Tele-Xenar 180mm. AF would place additional constraints on a lens design so I have no trouble believing this to be true across the board with manual vs. AF designs.
So there's all the data I have--I would love to sit down with one of the lens designers and just get this answer settled.
My subjective take: This question has been asked many, many times and hasn't been answered by the manufacturer for 3+ years. I can only believe that the difference isn't really very large. On the other hand, with a 5.2 micron back coming online soon, perhaps we will soon be able to see a difference between an AF and AFD (assuming an AFi-II 12 gets made), but I think not--they'll continue to be indistinguishable.