I bought one of these used about fifteen years ago on an impulse because of the low price. I haven’t used it for many years, so this may not be a terribly helpful reply, but this is what I can say....I bought it partly because I was interested in trying out the SF feature, and partly because I thought it might be a useful light telephoto lens in a minimalist travel kit. neither use panned out well, though that may be me rather than the lens. I never got results with the SF feature that wowed me, though portraits aren’t really my photo style. I have never had any interest at all in the f/2 or f/1.8 versions of this focal length, so I can’t claim to be a typical user.
As part of a light travel kit, without IS I never really felt happy using a lens of this focal length without a tripod, so that never worked out. I remember that the lens was very light for its size, but always surprised me with how large it was when I pulled it out and considered taking it on a trip. Autofocus speed was fine for my landscape and travel uses, but not impressive for speed. As you’d expect for a lens of this weight, price, and vintage, build quality was not impressive. The last time I used it I was shooting a Canon 1Ds, and image quality was fine on that camera. I wouldn’t count on it being satisfactory if you pixel peeped on a modern full frame, but don’t really know.
Sorry this isn’t a more helpful reply, but I suspect you won’t find a lot of users of this lens now!
I don’t think it ever really clicked for a lot of people.