I love these variable ND filters. While 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 carry a whole set of filters with you.
This takes up space, weight, and is, of course, more expensive. Changing them or choosing the right ones on-site is also time-consuming.

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

You have to pay for this advantage with a slight loss in imaging performance.
Since such filters essentially "only" move two polarizing filters in opposite directions, there are slight inaccuracies in the uniformity of the darkening.

However, this can be corrected relatively easily in post-processing.

Otherwise, there are no weaknesses, at least not that I—as a layperson—could identify.

For me, the advantages and user-friendliness clearly outweigh the disadvantages.

Thanks to the "handle," it's actually very easy to use. The resistance is also just right, so the desired setting doesn't change easily.

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

I give it five stars!