Workes very good, can recommend it to anyone.
However, I'm not using it anymore at the moment, because I somehow wasn't able to use any browser theme with it. Maybe I'm just too incompetent to find the right setting, but I if you want to use your usual Firefox theme I'd tell you not to use this.
But, as I said, I'm very impressed by the quality of the CSS filtering, and if you just care about that you should definitely give it a go.