I did some tests with advanced bokeh settings, tried to find optimal values. I think that for most realistic results i will try to stick with 0 - 0,7 range for center bias and -1 - 1 for vignetting. It looks like at more extreme vignetting values, image corners starts to resist to blurring - something i never noticed in real photographs. With center bias set at 0,8 and more, bokeh starts to resemble image taken with mirror lens and negative values just gradually brings everything back in focus.
Attaching set of images with vignetting set to 1 and 1,5. At 1,5 cat's eye effect is more prominent, but image corners looks really bad.