I have the non-Kaeseman, non-slim version on my 24-105. Not sure what body you have, but on my 7D there is no vignetting. I stack a 0.9 ND filter (also B+W) on it and still get no vignetting. I do think they're worth the money. If I have the sun in the frame with stacked filters, I occasionally get some flare, but more often I don't. And if it is there, it's so minor that it's trivial to remove it in post.

I've also shot with the 10-22mm with the CPL and had no vignetting, but you have to be really careful with the CPL at that wide angle. It's easy to get banding in the sky with the CPL.