I guess that the comparison of the maximum apertures would be relevant if the S2 were a real MF FF camera instead of being a mere APS version of MF.
there is a disconnect here and you don't get it... first off, MF refers to Medium-Format right?.. and Medium-Format is from to the old days of 120 film.. if a camera took 120 it was medium format, 35mm film was small format and sheet film was large format..whether you used a handheld 4x5 graflex rangefinder or 11x14 view camera, Hey, guess what?... flim is off the commercial table now.. not relevant...done!..commercial digital cameras range from 4/3rd sensors to almost 645 80mp sensors.. seems to me that the S2 sensor size is in the middle somewhere..however I would say that it produces image quality in the old "Large-Format" range, so your comment inferring that the S2 is not up to "MF" is just a full frame of BS..Image quality matters above sensor size.
I know there are guys(no girls would do such things) who spend a lot of time and effort trying to compare an 8x10 piece of film to the current high end 80mp and smaller multi-shot sensors and they are amazing and have replaced Large-Format work. Also by using your MF FF definition a sinar p3 tech camera with 16mp digital back is really not "medium-format" either..please!Enough!
It is pointless to keep using these old film-era monikers.. for hand-held shooting you really don't need anything better than what the S2 provides..and it does provide it at f2.5 with a sensor/lenses twice the size of traditional slr cameras.. German glass has always been had at a premium, before AF, before weather sealing, before electronic leaf shutters, before our weak dollar. Leica S2 lenses offer this, if you want to be shocked, try their cine lenses.. simple yet elegant manual lenses that won't even cover the S2 sensor @ around 20g per lens.. oh yeah, you have to buy it in a set of 8 focal lengths.. so, in comparison the folks in solms likely think that this AF 30mm is a deal.
Sadly too few photographers sell their work in a smart business model making the sting of new equipment less painful. I know it is an old argument but do the math on a years worth of film and processing in the old days.. most guys would say it was in the 5 digit range.. a year..if you're shooting digital now and are not billing for digital capture, etc.. that is just too damn bad..and that new sensor/camera you want to upgrade is just going to hurt.
If you want the old quality of medium format film.. you can get yourself great camera like the contax or other and relive the 120film days of glory..But if you just want the old "medium format" price point, I personally think that both canon and nikon digital solutions have filled this area very nicely..and improved on what I use to get from my hasselblad 500cm shooting film. This is the new "medium format"..the cameras that do the mass share of commercial work. The high end hasselblads and this Leica are not for the masses.