Initial results from casual "real world" (if banal) shooting... It was manually coded in the MENU as an Elmarit-M 21mm f/2.8 (11134). No off-colored edges and only very slight (if any) vignetting wide open as a result.
Distortion is remarkably low and well controlled. Impressive. Perhaps slightly barrel.
Sharpness is good from wide open; not quite as good but surprisingly similar to f/4 in center. Even at MFD (.7m) wide open, it's quite nice and very usable. Perhaps not "wow" sharp like the ZM or SEM however.
Fairly even purple fringing across the frame wide open on strong backlights/contrast transitions. Not unexpected and even the $11k Noctilux does this (if not more so). Cleans up by f/4. Some CA wide open (in the bokeh as well) but not bad.
It's hard to get a handle on the bokeh since so little is actually OOF with a 21mm... But it's got some of that "Bokton mojo" going on. That is, nice - like the 35mm Nokton. Perhaps not quite as smooth... But most definitely unlike the 50mm Nokton... Which is unpredictable and generally kind of nasty (when it's bad).
This should not be construed as even remotely scientific testing. In fact, it was quite half-assed. But the weather and lighting has been crap. Stay tuned.