In my opinion I would put cold frozen hands in the same category as bad fitting boots. Seriously, freezing hands used to ruin my fun on the hill until I finally slipped some Swany Toasters on.
These mitts operate with the layering principle to keep warm; they include a base glove, and a shell mitt. As is this combo is pretty warm and waterproof. I've had these mitts since before I joined Newschoolers however and wore the inner glove out.
I swapped those out for some home depot dipped working gloves and have been seriously impressed at how stellar of a combo they are. Extremely warm, and if the mitt's palm wets through, the rubber on the glove keeps your hands dry for very long periods of time. The stock setup works good, but I'd highly suggest the dipped glove as a liner.
Durability wise, like I said I've had these mitts for a very long time. They've been through anything and everything, and I plan on skiing in them next season. When they die they will be replaced with the newer version.
Functionally the mitts are pretty awesome. They have a side zipper running along the index finger which can be very nice for accessing the insides of coat pockets, or for just venting the mitts on the hot days. The only thing I'm not super thrilled on is the cuff. It's one that's intended to go over top of your jacket sleeve, however I prefer mine inside. For how awesome the rest of the mitt is though, this is a compromise I'm willing to make.