I have used them in the past as well. I ride all year long only with a half helmet even in these Upstae NY winters. I felt that the mask worked well, but it did fog the glasses. I also found it to be a bit uncomfortable during longer trips as your face warms up, or the moisture from breathing dampens the mask. Once that happens you get all wet and the mask can start to smell. Little gross. But, it does keep you warm. Since I kind of enjoy the cooler temp, I started wearing Schampa full face masks. They are thinner, leave a nice opening for your eyes and glasses, yet still allow air movement while you are riding. I find that this mask actually provides more coverage in the neck area, and I can easily move it around if need be while riding. One other bonus I find too is that since they are a full head mask, my ears and head stay warm and since the material is thin you can still hear great.
Not to mention, the ones I use have the skull face printed on them, and all the kids in the cars get a kick out of it......