I have a Kobalux 28mm/3.5, and I love it. I don't have a CV 28mm lens to compare it with, but I have the 28mm/2.8 Rokkor and the 28mm/3.5 Canon. Each of these three 28mm lenses is first class. The Canon is low contrast and high resolution, the Rokkor look is similar to a Leica lens look, so it is higher contrast and high resolution. The Kobalux has a somewhat special look, with very high resolution and medium/high contrast. Maybe I am wrong here, but this is what I am seeing in my photos with these three 28mm lenses.
Dante Stella compares the Popular Photography results for SQF the 21mm and the second version 28mm Kobalux with the Heliar 50mm/3.5. Both 28mm lenses are very sharp.
"And compare these to the 50/3.5 Cosina Heliar (below, tested 5/2002), which is Pop Photo called the greatest prime lens ever. I can't say what SQF is (other than Subjective Quality Factor), but whatever it is, both Kobaluxes hold their own with the best."