Dan, I've never done a direct comparison with a 'better' coated lens of a similar focal length. To look at, the Lustrar coatings are pale and mottled, particularly on the inside surfaces. I have two of these lenses and both have similarly unsexy looks.
The 18" is my most-used lens, and it's not often I get unexpected or objectionable flare with it. I do use a lens hood (a Lee compendium fully extended) but I try to avoid having to carry an extra bellows and intemediate standard, so quite often the camera bellows is barely pleated and some bellows flare is inevitable.
It's better than my 6x6 Kowa lenses which I use without a shade, but worse than my unshaded multicoated Pentax 35 mm glass. 4x5 photos taken with my multicoated 90 mm S.A. or 150 mm Sironar-N of the same landscapes in the same light (inside the same lensshade) do have the edge in clarity and snap, despite taking in more sky.
The lens is sharp. Looking at even flatbed scans of my negs is like using 10x binoculars on the scene itself. I'm not very interested in sharpness per se, but the APO-lustrar is pretty amazing. I assume other well-made dialytes would do as well.
One other advantage of these over the 480 Ronars is that the 18" Lustrar will fit, just, on a Technika board, which aids usability in the field. I'm not saying it should be a cult lens, just that for the price (mine were £80 and £10) you get a lot of performance.