Yes, I own and use one of these. Some quick remarks:
-- Focusing accuracy is no problem at all on a Canon 7.
-- I never tried it on a P because the P lacks an 85mm finder frame; I'd guess it might be a bit dicey, at least at close distances and full aperture. I say this based on using it (with an auxiliary finder) on a VI-T, which has the same RF baselength and finder magnification as a P; on the VI-T, you can switch the finder to a "magnify" position, and this gave me more confidence in its focusing precision. Still, your visual acuity might be better than mine, and you might be able to use it on a P with no problems.
-- The images it produces aren't trashy at all, if I understand your meaning of "trashy" correctly as referring to images with very characteristic optical "artifacts" such as flare spots, haze, distorted out-of-focus highlights, etc. (In some cases I really like these artifacts -- they give a picture a definite '50s-photojournalism atmosphere -- but not everyone enjoys them.)
The 85/1.5 doesn't do this to nearly the extent of some of the more extreme ultraspeed lenses (the 50/0.95 being the most drastic example.) Its images look pretty "normal." Compared to a modern lens designed for lab-bench "sharpness" (my 85/1.8 AF Nikkor, for example), details are somewhat mushier, contrast is lower, and the sharpness goes off somewhat in the corners -- but it doesn't look strange or call attention to itself. It's noticeably less crisp than my 100mm f/2 Canon, and likewise would be the same compared to your 85/1.8 Canon. But it's not bad, and certainly you can get "usable" images with it. I think its look at wide apertures is somewhat similar to that of the Canon 50mm f/1.2, which many people admire.
Lately I've been trying it out on my Epson R-D 1; below is an R-D 1 picture to give you an idea of what its fine-detail rendition looks like. The upper image is downsampled from a somewhat cropped R-D 1 frame, the inset below it shows the original area at 100% pixel-for-pixel size.
-- In terms of handling, the 85/1.5 isn't as huge as you might think; it's hefty (1-1/2 lbs.) but not all that much larger than normal -- about 2-1/4 inches in diameter and 3-1/8 inches long at infinity. The biggest irritation about using it is that, as with most older Canon medium teles, it focuses via a single helical, meaning the f/stop ring rotates as you focus. Two more minor irritations about that f/stop ring: unlike your later 85/1.8, the markings aren't equally spaced, making it difficult to set intermediate f/stops at smaller apertures, and the knurling isn't very deep, so it's sometimes a bit hard to grip.
If you're looking for a lens to make softly glowing portraits, I'm not sure the 85/1.5 would be your best choice -- its "signature" isn't that pronounced -- but if you simply want something with more moderate contrast and less harsh detail definition than a modern lens, it might be just what you're looking for. They're kind of expensive on the used market, though, so a try-before-you-buy option would be worth seeking out if you can.
Hmmm, file attaching doesn't seem to want to work today, so I'll host the example picture on my own server. BTW, I recently posted this same sample to a thread on the R-D 1 forum, so apologies to those who have seen it before:
