I haven't had the change to do real world testing yet but I've taken a few test shots in my garden to check for loss of sharpness and color casting. I used a macro lens for checking fine detail and wide angle to see if its consistent across the frame. I also checked it against my Lee Filters big stopper.

I couldn't find any percievable loss of sharpness across the entire frame with the macro or wide angle.

There is a bit of a color cast to it from looking at the exif data but shooting in raw the camera adjusted it out for the most part and can be edited out manually if required. Importantly though it seems to be consistent across the entire frame, even at 10mm on my apsc sensor.

I did experience vinetting on the wide angle (both 10mm and 22mm) but again it can be edited out very quickly in lightroom.

It would have been nice if it came with a light gasket supplied with it but for the massive price difference compared to the bigger brands I can forgive them for that. They can be purchased online elsewhere if required which is what I'll be doing.

Overall I'm pretty happy with it, which is just as well really as it managed the slip through my Lee Filters folder when I wasn't paying attention and drop onto the paving slabs in my garden, which chipped the corners of the glass. That's my own fault though as it's a known issue I have with the holder, I experience the same problem with my Nisi filters in my holder so I think it's a bit worn out.