I have tried it so far with APX100, Tmax100, Tmax400-2 and Acros - not systematically, but I know these films quite well, and try to make some general assumptions (purely visual) based on my experiences.
First, it is not a super-fine grain developer, but "fine grain" (and I am not aware of any actual film developer that is not called at least "fine grain"). It ist defintively not in the league of Perceptol, Xtol or A49 regarding grain. I would say that the results of Mr. Böhr with APX100 are not typical. I ordered the developer based on this this, and I have to say that I do not like APX100 in EFD. The grain is well defined and even, but not as fine as in the classic solvent-type developers.
It does give full speed (or maximum 1/3 less; the Moersch datasheets are very detailled and reliable), and where it really shines is the exceptional definition it can produce. I developed an Acros 100 (120 format) and the prints really look fabulous with tremendous detail and a very stong "3-D" impression. I also did a Tmax 100 (35mm) in EFD, and while the tones where very nice, I did not like the grain in a 20x30 print (especially in the brighter greys). It was not bad, but if one uses Tmax100, he is usually looking for grain-free 35mm prints.
In short, it should be a really fantastic developer for 100ASA films in medium format, it can be great in 35mm and slow films if you can somehow compromise on the grain (again: it is not bad, but it's not Microdol or Xtol), but I would not recommend it for faster films (except you want the "high-definition, defined-grain" look).
IIRC, in the beginning it is only available from the Moersch online shop. I guess Mr. Moersch is testing the market before sending out bigger batches to other distributers.
Georg