I bought bar mitts last year (medium) for my husband as a Xmas present, and he really liked them. He uses them on both his cross commuter bike and as the captain of our tandems.

So this year I saw that the red and blue ones were on sale for $45 ($20 savings) and bought a small pair for me. So far I've only used them on the tandems (stoker) but they've been great. No, I can't easily ride in the drops so we lost a little power on the hills. It's easy to remove my hands to signal turns, slowing etc (but I don't want to because my hands are so warm inside).

We rode the Lorain Wheelmen Red Flannel ride yesterday and thought we'd need to have post a guard to watch the tandem at the rest stops - so many people were eyeing them enviously! They are a great investment if you plan to do a lot of winter riding.