Love them! I rode with them for the 1st time yesterday in -5 weather, and my hands were nice and toasty.
I've tried several different gloves and mittens, but none kept my fingers from painfully freezing. I bought them because, on my recent trip to New York city, I noticed all the bike carriers used bar mits. Most of the mits were permanently taped to the handlebars and highly worn. That convinced me to get a pair. These guys ride all day and spend hours on their bikes year round.
I'm not hesitant to ride on the cold days now.