I absolutely love this filter. I took it to the ND filter battleground, the Bonneville salt flats of Utah. It was a very bright sunny day. Below are the stats of the attached pic. Straight out of camera with only a exposure bump up in post to make it brighter. I shot dark to save the highlights.

Camera: Canon 7D
Lens: Tamron 85MM f1.8
F-Stop: 1.8
Shutter: 1/8000
ISO: 200
White Balance: 5100K
ND Filter: Max

I'm set this filter to it's max setting to see if there was any issues to be found and they are miniscule. The chromatic shift of yellow tint is easily fixed in post and is much better than the harsh magenta/green shift of some cheaper filters. There is a slight addition to vignetting, but easily fixed as well. The clarity and contrast is minimally affected without much loss of sharpness. Nothing that a little bump in post can't rectify as well. The harsh light didn't affect contrast too much when shooting towards the sun either.
What impressed me the most about this filter is the build quality. It is solid and the rotating action is very smooth and holds its place. Even with me moving up and down it stayed where I had placed it. It really is a solid smooth action.
I really like this filter and it's an awesome piece of kit to have to get to the those low apertures.