I just noticed that darktable (1) export produces PNG (or TIFF or JPG for that matter) which are noticably much less sharp than the view in darkroom, looking more like the full size preview in lighttable.
The shots were taken under suboptimal conditions (dimmed conference room, moving targets), so they were in general underexposed at even 1600 to 3200 ISO. Using Profiled denoise (Nikon 1 J1) at somewhat strong settings for luminance.
I attach a screenshot illustrating my core options (as well as the fully zoomed in lighttable view), another one illustrating the darkroom view (much sharper, look at the wrinkles and the hair of the person in the foreground), and finally the 16bit .png, the .nef and the side car file.
Only possible workaround at the moment is screenshot and then crop in gimp. But that will not give me the full resolution ...
Since export is such a basic functionality, I guess this could be a show stopper for 1.6, unless it is just me doing something really stupid.