I have one of these on order since it looks like it might fit my need for a light, fast wide and because now I have a good (famous last words?) 24mm PC-E I don't need another 24.
Here's a link to an interesting set of samples, full size downloadable. The photographer Thomas Rubach has taken some care to make a useful set of images. I find it pretty good, reasonably sharp even at wider apertures to the edges, a lot of vignetting though. However, even at F5.6 there is an odd zone of less sharpness on the left hand third that is not replicated on the right. Take a look at any of the mid aperture shots but especially the F5.6 landscape.
Anyone got a view? Anyone tried one? Could be a useful piece of glass....