vkouznetsovwrote a review of Castelli Nano Shoe Covers on March 22, 2011
It says these keep your feet "warm, dry, and wind-cheatingly fast". Take out warm and dry. Even though they have the appearance of completely wind- and water-proof covers, my feet were soaking wet after riding in the rain. Haven't tested them in mid-season temps, but after a time trial hard ride in 34F weather, my toes were frozen. In addition, I have issues with their quality. The zippers don't always stay up (and they don't have a lock to ensure they do) and the material around the cleat opening started to tear from stretching after just 2 rides.