I'm pretty easy going about a lot of things, but the Vivitar stuff was good and bad, depending how you measured it.

Good, very good, compared to the other off brand stuff.

Nowhere in the park if you compare it to Nikon, Minolta, etc.

Thirty years later, if used much at all, it will be worn out. If it wasn't used, the lubricants will be dried up and will wear out when you begin using it. The lubricants are critical in these designs. Guess why they were less expensive than Nikon ? Not because Nikon was out to overcharge you, but because they built lenses to a higher mechanical standard. Kino, and all, relied on lower expectations of service life and lots of grease instead of brass, steel, and ball bearings.

Just one guy's opinion, of course