Context and Overview
I'm a newborn/portrait and wedding photographer. I have used this lens on occasion, with the crop-sensor D3200. "DX" refers to crop sensor - Nikon's full frame lenses have an "FX" symbol on them. This is a crop sensor lens and not likely to be useful on a full frame camera. This is a semi-wide macro lens, with focal length of 40mm, which on the crop sensor is actually a medium focal length. Max aperture is 2.8, which would be good for a zoom - for a prime, 2.8 is nothing exciting.
The lens has one of the three features I consider to be required to be a fully functional lens: it has autofocus. It lacks weather sealing and image stabilization.
But, as a bonus, it can focus down to macro distances. Unfortunately, the lens extends during focusing (it does not have internal focusing). The front element is deeply recessed and I recommend using a filter, simply to be able to more easily clear off condensation when shooting in environments with high humidity, or rapid changes in temperature.
Image quality seems decent. Macro lenses are typically pretty sharp so I always trust a macro lens to get sharp images. The photo of the shawarma platter was taken at f3 (close to wide open) - it does not blur out the background nearly as much as a 50mm f1.8.
This is why I recommend using a filter - the photo of the bird is foggy due to the condensation buildup on the front of the lens. If there was a filter on there, I would have likely wiped off the filter and got useable shot. The front lens element is really recessed, making it less likely that you will wipe condensation/rain/ocean spray off of it.
Autofocus in bright light is decent. In low light, it's very slow.
Overall, this is a relatively good lens. Personally, I would prefer one of the Nikkor FX f1.8 prime lenses as they at least have some weather resistance - they have an o-ring/gasket at the lens mount. And they have a wider aperture. But this 40mm 2.8 has the ability to focus at macro distances.