The mechanical build quality of my 17ers is that of (my) 2.0 / 12mm in nothing. The snap-focus ring works just perfectly, despite the slightly lower width. It can thus work even better in the end, because the manual focus is stepped substantially finer than the 12er.
Visually, there is of course really a little room for improvement. The lateral chromatic aberrations are limited, but the longitudinal are quite pronounced. This is in such strong light optics though nothing unusual. Compared to the 2.0 / 12 and 1.8 / 45, the longitudinal error of the 17ers at maximum aperture are but quite clearly.
In contrast, and resolution I would agree with some of the previous speakers quite possible that the Panasonic 1.7 / 20 is a bit better, but not so much that I would prefer. This has mainly to do with the operation of Olympus cameras. The Olympus 1.8 / 17 focused much more quickly and silently. That has always bothered me at 1.7 / 20.
Also, I'll personally with the 17mm focal length doing exceptionally well. This really is the proverbial "always-on" objective. The opening angle approximately equal to the natural field of vision, so that there is rarely surprises when looking through the viewfinder. The picture is just right always. I would not have held a long-time photographer for possible zoom. And even with the aforementioned 1.7 / 20 I have not seen such.
In my opinion, the ideal standard lens on the OM-D or PEN camera. Complemented by the outstanding 1.8 / 45mm is an ideal basic equipment.
