Not too much I can add that hasn't been said already in this thread. In my original post a number of years ago of Pentax 645 lens tests and also since then, I've tested numerous samples of this lens and consistantcy in performance between samples is fairly close. Whereas the short end of the zoom is exceptionally good and can be used at apertures wider than f8, the long end benifits from stopping down considerably more.
I'd say excellent samples of the zoom at 85mm are mealy good-very good but performance appears to fall off somewhat beyond 65mm as pointed out.
Again as noted by others, the zoom is substantially bigger and heavier than the single focal lenses it its general range. No doubt the new zoom when released will excel much like the current 28-45mm zoom but at what expense and size.
With regards to Joe's post above in viewing his images taken with this lens....not sure what specific info it will yield as all of Joe's photos taken with any lens (or camera) including those taken thru coke bottles, are always pretty spectacular.
Dave (D&A)