The "Splats" that Rivendell has produced turned out to work pretty well in the cold. They are intended to keep your feet dry in the rain, and I suppose they will. After seeing them mentioned on another thread, I wondered if they might help with wind chill for those of us in the frigid areas. They seemed to yesterday. I am putting some more pics and detail on my blog, but I rode about 6 or 7 miles with them on in 25-30 degree weather, and took them off for the return ride. While I can't say that I was "toasty" comfortable,my feet were noticeably colder on the return. I think they will be useful in colder temps and it would be conceivable to add a layer of fleece to the underside to help trap the heat in, they are really easy to take on or off which makes them a lot more practical than the old "booties," although neoprene "boots" will definitely be warmer.