The AIS 28/2.8 focuses much closer...

Thanks Roland. Maybe, I'll find someone who complains about autofocus not working on their 28mm/2.8 AIS

I know the question is too generic, but all in all do you think the difference between 3.5 and 2.8 is worth the effort of getting the later one?

The AIS 28/2.8 focuses much closer - down to 0.2m, compared to 0.25m for the AIS 28/2, 0.3m for most other 28mm models, and 0.6m for the old Nikkor-H(C). The AIS 28/2.8 will give magnification of 1:3.9 at close focus, so you could almost consider it a wideangle macro. If you mostly shoot landscapes the closeup performance won't be of much importance, but the ability to focus close does make the lens more versatile.

The AIS 28/2.8 also has very low geometric distortion - straight lines are rendered straight right to the edge of the frame. The AI 28/2.8 is similar, it has a similar optical design but without close range correction (CRC), so it does not focus as close or perform as well at close range. All the other 28mm lenses have some barrel distortion which could make them less suitable for architecture or seascapes.

Very limited internet page, one really need to know for this to work, I guess he likes to keep this service low volume sales...

I just wrote him an E-Mail and recommended to upload his catalogue as pdf-file.
As far as I can see he tries to balance his efforts to have some revenue but is not willing to run big business any more as he is in beyond retirement age - and he is more of an technical enthusiast enjoying solutions for practical problems than a merchant.

He also serves as a distributor for selected other products. I aquired first my Sachtler ENG-2CF and then a tuned and modified  Sachtler FSB8fluid-head from him

The Brad Hill report sounds very promising
Just suffering from the reported reduced burst length ;-)

Two inconsistencies I found:
He is praising the "Recall Shooting function" (which sounds fine indeed) giving the example switching from macro work crawling on the ground and switching by one button to shoot the red-tailed hawk. He probably would have to switch lens too in this case.

He is reporting the ability to customize AF-ON function to the horizontal subselector  to do AF-ON and AF-Field selection without having to switch between AF-ON and multi selector as if that was new. Don't know about the D5 but I can do that with my D4S already. I just found the sub-selector way less comfortable for each function so did not get too familiar with that approach.

I would not see a TC index in the viewfinder as crucial if I owned the 180-400 (wouldbe nice to replace my 200-400/4  with that lens). This lens is indeed overpriced, but even more so is the new 120-300/2,8 (it hasnt got a TC btw and is the new pro lens that Nikon has paired with the D6 which is somewhat against the theory of being more TC lenses soon. Nikon made the 180-400 TC to be on par with Canon who has tried to beat Nikons (for long years standalone) famous 200-400.

Hopefully the new AF-system will be cloned in the future as it was in the past. I would like to see a D500 successor with this System

that is a VERY FINE racing shot!

+1