I've been riding the Fasterkat boots (rated down to 25F). Very, very comfortable, warm and excellent riding. An hour of riding at 25F and my feet have been actually warm. I would have no concerns about doing 3 hours with them. I bought them nice and big; the secret to keeping any shoe warm, but the shoe is so well thought out for cycling that the surplus room inside isn't an issue. I never felt like I was sliding around. Another plus: my feet don't sweat in them at all, either while riding in temps up to the high 40s or indoors. Socks stay clean!

Oh, I am a skinny guy, 155 pounds with very long arms and legs and I have near frostbitten my feet many times growing up in skating country. Very cold feet are a fact of life for me. Finishing rides with warm feet is a new concept!

I give those boots a 10. I'm guessing their colder varieties are also pretty darn good. (Actually, a nine, only because I really wish they looked like my all-time favorite hiking boot, the smooth leather Vasques, back when they were made in Italy which were for me, just as comfortable and I really liked their looks.)

Ben