I have a late serial-number copy (in the last batch of 10,000, probably from the final year of production in 1985) and it has very good focus stiffness and no zoom-creep. I think they (mostly) fixed the issues later in production, but of course I might also just be lucky! It's a lovely lens, and in fact my only zoom lens. It is a great design, both optically, and also just utility: Small and light, with a very useful portrait range.