I had the Vivitar Series 1, 135 f2.3 with Nikon mount. I used it very much on my Nikons and remember it as having exceptional focusing due to the helical threads being designed so that it took forever to go from close range to infinity.
When I bought a Nikkor 105 F2.5 I realised how good the Vivitar focusing was. The Nikkor was/is quite good, but the focusing movements required careful hand movements to get accurate focus, by comparison to the Vivitar.
Unfortunately I was relieved of the Vivitar by professional thieves who used a removals van backed up to the house and removed everything I owned, except for my homemade double bed and my television set, which was faulty.
Everything that Wayne says about the Series 1 lenses is true. They really were a superior aftermarket set of lenses.
They also made quite a good colour enlarger, which I believe they actually manufactured, instead of re-badging some other manufacturers unit.
In the late seventies and early eighties, their products were regarded as up with the best.