I’ve had a couple. The one I still use is terrific, and it was my go-to lens on the K1 for walking around until it was replaced with a FA28-105PZ
I tested it against a couple of FA28-80s, the PZ28-105, the 35-70 f2.8 AF, and a couple of old primes.
The 35-70 was better than either of the FA28-80s, tied the PZ over the relevant range, was beat by the 35-70 f2.8, and was a mixed bag with some cheap third-party primes. (One of the Vivitar 28s was very good. The others, not so much...)
That said, the FA28-80 Al wasn’t as bad as the other one, and neither was garbage. My PZ28-105 beat the 28-80s but got some haze in it, so I replaced it with the DFA28-105, which is noticeably better than any of the older lenses.
I have had a couple other F35-70s. One lives on a SF10 and seems fine the couple times I’ve used it. The other wasn’t very good, even before it completely came apart in my hand... that may have been related.
I have to think the sample variation with inexpensive lenses is enormous, especially 30+ years on...
So I’ll believe results consistent with mine that show it one of the best values going, but I’ll also believe there are a couple still out there that are horrible but have not yet been destroyed
-Eric