I've had mine for a few years. It does an unbelievable job of protecting the Rear dee. Keeps it looking and performing like brand new. I also, haven't had any problems shifting in frigid temperatures. But I also grease my cables inside the housing. And I think that has more to do with it than the Grunge guard.
And in answer to the OP. I prefer the different gears in winter as opposed to SS. The variety comes in handy for different road conditions.