Well, I owned this lens right when I was starting out with RFs and found it pretty difficult, but it is such an amazingly unique lens I always regretted selling it pretty quickly after purchase. So I wound up buying a new one today on eBay to see if my skill and patience have improved enough since the "beginning times" to take advantage of this w i d e lens.
My thinking is that it will make a great second three lens set: 12-35-90 to contrast the 21-50-135...all that remains to be seen, but I will post a new lens sample section as soon as I have a few rolls down.
Here's one from a few years ago: