As a professional photographer, filters are a very important part of my kit and I use them nearly every time. I own the Okko CPL Pro, ND1000, ND64 and they are beautifully made. I highly recommend them.
Pro CPL - Great level/range of polarizing. Saves on editing time and takes the glare from the windows. Frame is thinning than others I've used. Shooting some more cars this weekend for a magazine.
I had just purchased a new lens and an Okko ProUV filter. Dropped my camera smashed my filter but saved my lens. A free replacement arrived the following week.