Al, I agree. I had two of the original Hologon's. One for 6-8 month when it came out in the early 70's - late 60's. Interesting lens, but very impractical. F8 as the widest (and only f-stop) and f18 if you didn't want solid black corners. Not useful for editorial/press work!
Later I picked up a used one (early 90's0 - rather pitiful state, but it only confirmed my past experiences with it).
It is a hyper focal lens and really does not focus to infinity. It has some use for doing architectural models and "drama" shots.
The Heliar is optically a better lens as it will focus and also give you a choice of apertures. The, new, coupled one also has an advantage as it will take 52mm filters and is coupled. AS most Nikon F users - I have a box full of 52 mm filters, left over from the 70's-80's. I think there is even a "star" filter among them. Remember those! OK, that on a 15 would distort the world view substantially!
The ZM 15f2.8 is impressive for its speed, size and price! Performance is very good, but at that price - it should have been coupled!