For its price (100€), it is indeed very good as the other reviews say.
For videos, it doesn't perform well. The auto focus seems to work when changing the contrast of the scene. This means that if you try to shoot a video of a person, it won't come out right because it doesn't focus if you choose the tracking mode or even if you use face priority! The camera detects the face, but the lens doesn't automatically focus! As a result, if you press the button to focus, it has to go through a process of blurring, unblurring, blurring again, and then finally focusing.
Manual focus works well if you have an external monitor (or if the camera has a good screen) because of the smooth ring it has.
For photos, it's okay but you will need to take 3-4 burst mode photos because if you take just one, it will come out slightly blurry due to the lack of Vibration Reduction. Also, clicking twice to refocus (even if it had already focused) helps a lot because it doesn't always get it right on the first try.
Sometimes at night, even though it seems like it has focused, it makes some slight noises without allowing you to take the photo, resulting in missing the moment and looking somewhat off...
However, for a first lens (excluding the kit lens), it is quite good. It gives that "professional look" that many people want at f1.8 with nice bokeh and a nice image if you manage to get it in focus. Given that it is a prime lens, you will have to move towards the subject.
Long exposure at f8 highlights the 7 blades it has, and since it is the sweet spot, it has the best possible sharpness, even in the corners.
It is generally brighter than regular lenses, and the camera doesn't realize this, so you will have to adjust the exposure compensation to -0.7, otherwise there will be overexposed areas that shouldn't be there!
It causes vignetting at the edges, which is not clear until you do lens profile correction in Lightroom.
It has significant chromatic distortion at f1.8 if there is intense light, which cannot be corrected with lens profile correction in Lightroom.
Keep in mind that it is not easy to find a lens hood for this lens, and it will give you some trouble until you get used to it.
If you have 200€, get the equivalent Nikon f1.8g lens as it solves the autofocus problem mentioned above and has slightly better image quality.
If you don't have the 200€, get this one and learn it. It will make you better!
Press that it helped you and let others see it!
UPDATE about 1 year+ later:
This lens was "gifted" as I bought the Nikon DX 35mm f1.8.
Conclusion: for an extra 50€ that the aforementioned lens costs, it is worth it. The Yongnuo lens produces a strange, slightly washed-out image in terms of colors and contrast, which requires a lot of work to fix and still doesn't yield good results.
Do not buy it. Buy either the 50mm f1.8 or the DX 35mm f1.8 from Nikon