These gloves work nicely on my rides below 20 degrees F. My hands stay warm, the gloves block the wind well. It takes a little getting used to having two fingers touching in the glove. I've never worn mittens, but I can appreciate the extra warmth keeping my pinky from freezing.
I suffered with frozen fingers for two winter seasons of commuting before getting these. I have a 30 minute commute in New York City, temps don't drop super low here but can often get in the low 20's. These are the best gloves I've ever owned. So far no additional glove liners needed, and no frozen fingertips.
A week or so ago I went out for a ride. 20F, 10 mph north wind. After 15 minutes of riding my hands were beginning to hurt. I found these $XX gloves kept my hands no warmer than a 20 dollar pair of gloves I purchased at WalMart. In the last month or so I have ridden several times when the temps were between 20 and 30 while wearing the WalMart gloves. After 30 minutes or so my hands would begin to feel cold in the $XX gloves. So I decided to try the $XX Pearl Izumi Super Glove. There is nothing Super about them.