I love these variable ND filters. Although they have clear optical disadvantages compared to fixed ND filters, the advantage lies in their literal variability.
With “fixed” ND filters, you always have to bring a whole set of filters with you.
That costs space, weight and is, of course, more expensive. Switching or making the right selection on site is also complex.

With a variable filter, you don't have these problems. Simply screw on one filter, turn it until you have the desired darkening, and you're done.

You have to buy this advantage with slight losses in imaging performance.
Since such filters in principle “only” move two polarizing filters in opposite directions, there are slight inaccuracies in the evenness of the darkening.
However, this can be corrected relatively easily in post-processing.

Otherwise, there are no weaknesses, not in any case that I could identify them - as a layman.
For me, the benefits and ease of use clearly outweigh this.

Thanks to the “handle”, it is actually very easy to use. The resistance is also right, so that the desired value is not so easy to adjust by itself.

Everything is fine here, even the price is right when you look at comparable products.

I give it five stars!