I ordered the ND filter because I want to play a little with long exposures (waterfalls etc.). I use the filter is not so regularly and so I am glad that I have not bought for 100 euros.
The quality of the filter I'd go with "good" call (but I have no comparison to the much more expensive, for example, by B & W).
The filter is stable and well made and comes in a simple plastic box. He swallows about 10 Blendenstugfen and is easy to assemble.
The image quality is for my needs absolutely fine. In the 1: 1 view of the LR can however detect slight dark spots or clouds. This hike also from time to time when I use the filter.
Continue do not bother me because I the images do not end in me 1: 1 look. But it could also be an isolated case.
To try and play the filter is absolutely fine. For professional use I can not judge it.