Just an update on my experience of the Buffalo mitts. I've only been out in weather cold enough for them three or four times and never long rides so far, but two observations.
Firstly, they're slippery. Riding on the drops, my hands are slipping down. Not enough to lose control and be dangerous, but just enough to be a little annoying. It's probably partly dependent on the bar tape; mine is a woven cloth, which Specialized call denim though it's certainly not the stuff your jeans are made from.
Secondly, after only wearing them a couple of times, they have changed the way I position my hands even when I'm wearing gloves with fingers. Now, when I'm on the hoods, which is probably my most used hand position, I have my whole hand wrapped round the "horn"* at the top, with four fingers on top of the brake lever. Previously, I used to ride with my hand a little lower down and two fingers wrapped around the base of the hood, between lever and bar.
*Yeah, this means buffalos make me horny.
