I like it. It's not as sharp as some other lenses, but at under $500, the price is right. For these I was using a CP filter, but I usually use a Gradient ND filter.
It's a gradient so it's dark at the top and clear at the bottom. It doesn't have a level like a regular ND filter. I would say it's pretty mild though.
Oh. I was just looking up some variable ND filters out of curiousity. When I sold my old lens and camera I sold my ND filters with it. Need to get some more.