OK, does anyone have this filter? i have an inkling hwulex does.... but anyway, i have a question about it. It's awfully expensive.... what does this do that i can't acheive by stacking two circular polarisers, which is obviously what this is in a slightly more convenient design? i figured if i use 2 slim polarisers like the kenko pro1 ones, they should be roughly the same diameter as the vari-ND. so, where's the roughly $200 advantage? surely it can't be THAT much better quality?