I carry four batteries. One in the camera, and three extras because of that same concern. In whole days in snowy sub-freezing weather I have never run through two batteries despite the fact that I take many hundreds of shots and I do not keep the camera warm. With that said, I almost always have needed the second battery. If you plan to get an extra battery or two, there is no reason to not consider this a great camera for very cold conditions.
By comparison, my 7D would sometimes make it all day in sub-freezing temps without a need for a change, but at least half the time I started a second battery before the day was through.
