The copy I have is not in great condition. You can see the separation is starting at the edges with bubble like, small white dots. It should not effect the pictures though. The lens is cosmetically very clean and looks like it was not abused at all.
Metrocentre -- NEX-5N & Vivitar 35mm f2.8 [OM] @ f8
At around f8, the far edges still show some softness, but center sharpness is very good. It lacks the microcontrast of the very good/expensive lenses, but it's optically quite competent. Wide open you can also see some softness, which is quite normal for inexpensive consumer lenses, but the centre is still quite good.
Hot Dog Vendor -- NEX-5N & Vivitar 35mm f2.8 [OM] @ f2.8
For a cheap lens, the build quality is excellent. It focuses very smoothly and the focusing ring is well damped and very enjoyable to use. The 8-blade aperture is a nice touch that no doubt helps with a nicer looking bokeh, which i find not objectionable at all. Surely not the best looking bokeh either.
Yellow Tulips -- NEX-5N & Vivitar 35mm f2.8 [OM]
I think this is a nice lens to have. For sure, there are better 35mm lenses out there, and many are faster, but at what cost? This lens should be quite cheap and therefore good value for the money.