I used mine when in graduate school and was pleased with the results. Now my main rollfilm camera is a Rolleiflex 6008i with 50mm Distagon and that is one of the sharpest 50mm lenses out there, so it is not a fair comparison.
Recently, I got the Yashica and WA lens out and was using the WA viewing lens on on the Yashica's taking lens and shooting wide open. That gave some nice 'plastic camera' effects, without the troublesome plastic camera.