It is a fairly good lens for mainly amateur use. I have had it for about a year. The negatives are the poor build quality and slow auto focus in low light. The positives are the fairly small aperture (f/2). If someone (mainly an amateur) considers that they would have to invest 400 euros more in a comparable Canon lens, I would highly recommend it. In the store where I bought it in Athens, I had a discussion with the salesperson-photographer and he mentioned that compared to the Canon lens, he did not see any significant difference in the photos. However, I have not personally tried the equivalent prime lens from Canon.

Very good for its price. A cheap and reliable solution for use with the d3100.

-The closest focusing distance up to 0.25 cm, for capturing the unique sense of depth of the wide-angle lens.
-F2 large aperture, creating a virtual background, making the photo more enjoyable.
-Supports both autofocus (AF) and manual focus (MF) modes.
-7 aperture blades, allowing for shooting nearly circular diffused plates, effectively limiting the aperture to capture the 14-point star effect.
-High-precision chromium-plated metal construction, enhancing compatibility with the camera body, wear resistance, and corrosion resistance for long-term use.
-Lenses made of glass.
-Supports full-frame and APS-C format cameras, supports M/AV/TV/P and other camera shooting modes, and can display aperture data in EXIF information.
-Multi-coated lenses, effectively improving light transmission.
-Gold-plated metal contacts, effectively improving signal conductivity and corrosion resistance.

http://nikonrumors.com/2016/10/09/yongnuo-yn-35mm-f2-lens-for-nikon-f-mount-test-shots.aspx/

I use this lens on Nikon D600.
The quality in the center is average.
In the corners, it is the worst I have seen, it is really unacceptable.
Of course, I bought it from China for 88 euros, so I didn't expect much. I just wanted something wider than the 50mm at a reasonable price.

The build quality is surprisingly very good, as well as the feel of the focus ring.

I think the usefulness of this lens would be mainly for crop cameras that wouldn't use the lens's unacceptable extremes.
But still, there is the top-notch Nikon 35mm 1.8G DX.