I have to agree with Marc in the overall substance of his argument. I am an S2 owner. I have just two lenses so far, the 35mm and 120mm. In the past I owned a full Rollei system with both Schneider and Zeiss optics on a Hy6. I mostly shot film, but I also had a 22mp e54LV Sinar back for awhile. I shoot Hasselblad V with a 203FE, so I continue to own some of the best V system glass. The Mamiya 7II has taken some of my best photos, and I would say that performance wise, they are some of the best lenses available in medium format to this day. I have shot Nikon on 35mm, Canon FD, Olympus OM, a close to full kit of Leica R including the DMR, Leica rangefinders from the IIIb to the M9 with Leica, Canon, Konica and Zeiss lenses, 4x5 with Schneider lenses and probably a number of other things I am forgetting.
After trying all those, I can unequivocally state that the S 35mm and S 120mm are the best overall lenses I have used. Though I have not been in the S system for that long, the lenses continue to surprise me on just how amazing they are. It is not just resolution, it is how that resolution is maintained over the whole field even when wide open. It is how minor the distortion is for the focal length and how they often perform better at f/2.5 than other lenses at middle apertures. The character is neutral, in that they do not have aberrations that "add" to the photo like the Zeiss 110/2 does for a portrait or the Cooke lenses etc. They just render the scene the way it appears in person.
The only lenses I have compared directly on the S2 are the S2 lenses to the V lenses. I have only tried the 80mm CFE, 110/2 and a friend's 250mm f/5.6 Superachromat. The 80mm CFE has decent resolution at f/2.8, but is low in contrast and has lots of color aberration at that aperture, it needed to be stopped down to about f/8 to get close to the 120mm's performance. The 250mm Superachromat performed similarly to the 120mm in one test and worse in another. In practical terms however, it's very slow lens speed and difficulty in focusing on the S2 rules it out for me. One test had it at similar resolution and contrast, while the second showed it as lower in both contrast and resolution. Merits more testing, but in terms of use on the S system, the 180mm f/3.5 would be a no-brainer: AF, weather sealed, faster and likely similar or better performance.
From a pure performance standard, the 120mm Leica decimates the 110/2. With both lenses at f/2.5, the Leica is sharper in every area of the image, with less vignetting, less color aberration and higher contrast. The corners and edges on the 110/2 are mush, while they are still quite sharp on the Leica. The 120mm is even sharper on center at f/2.5 than the Zeiss is at f/8. I say this as someone who absolutely loves the 110/2 and the way it renders. But from a performance evaluation, the Leica beats it handily. It certainly does not fail from the bokeh standpoint either -- the backgrounds still look lovely.
So what does this all mean? I am sure that Phase's new lenses are capable of performing extremely well, and offering comparable performance at their best apertures. I would not be surprised if the Leica still handily beat them, given how they have done so with so many other great lenses and systems, I have tried. But at the end of the day, the overall shooting experience is what matters. This is where you need to test and figure out what you really want out of a system. For me, I wanted a very high resolution camera that I could use mostly for landscape and portraiture on location. I live in Iceland and often have to use the camera in bad conditions (while I wait for the good ones!), so having the weather sealing is a huge plus for me. From there, I appreciate the handling characteristics. If I were a studio photographer, I would have given more consideration to the Phase and Hasselblad cameras (though maybe still have gone with Leica?). These are the things you need to figure out based on your own work.
But why not a picture, after all these words. Not the greatest picture, but a good demonstration of the S2 resolution. This was taken wide open with the 35mm at f/2.5. I was amazed at how the S2 was able to keep from blowing out the highlights on the crane (which was brightly lit by strong lights on the dock) and still get a clear shot of the aurora, which is quite dim in comparison. The resolution is just the icing on the cake...certainly more than would be expected from a very wide angle lens wide open on medium format, let alone f/2.5 (the fastest of any wide angle on medium format).
Center:
edge:
By the way, this photo was not heavily post-processed -- there was no masking or selective editing. There was some recovery and exposure changes in lightroom, and basic sharpening. The surreal look is more from the artificial lighting on the dock and the way we are not used to looking at night scenes as being bright...basically, the camera sees more than we do.