It probably depends what focal length it is.
Anything 25mm and below will vignette quite badly.
I have a 25mm (Kodak) which vignettes, but the images it makes are still very nice to look at.
It is based on 4 glass ernostar design, new old stock condition, no usage trace.
silk smooth iris and focus, glass transparent and clean.
balck color and green marks give stronng feeling of modern photogrpahy, perfect matching to lumix SLG camera body.
Almost new old stock condition, very clean , 100% coverage on sensor, with inifinity focus.
Smooth iris from f1.9 to 22, focusing down to 60cm ,good for application on Panasonic Lumix GH1 G1 / / Olympus EP1 Ep2 micro four third system,equivalent to approx 50mm angle of view view in full 35mm frame scale
It's probably very nice yes.
Almost certainly will vignette to a varying degree at most f stops, based on my 25mm Kodak experience.
The attraction of the c mount lenses is their speed and the quality of the lens at a reasonable price.
I wouldn't pay more than you would a good quality standard lens at 25mm, f2.
I'm no expert, but the easiest answer is different.
The panasonic pancake is highly acclaimed. I don't yet own it.
The Kodak 25mm I have produces very high quality images, but you couldn't use it for standard imaging because of the vignetting.
It's a great fx lens, say for an arty film or music video.
Again, I'm no professional movie maker or photographer.