Buffalo Pertex mits are pretty good, but they have minimal protection when the temperature is really low, the weather is bad and you are stationary for some time.
Buffalo Pertex pile equipment are fabulous as long as you can keep your body core temperature at a constant level, ie keep moving and retaining body temperature.
I can remember an article in one of the very first issues of Trail Walker many years ago, where Hamish Hamilton, Buffalo's inventor jumped head first from a boat into Crummock Water in mid January.
He was able to get to dry land very quickly and move around, thus maintaining his body temperature.
The thing with Buffalo mitts is when their saturated with cold water, they offer little protection from the elements.
They really come into play, when the weather is really cold and dry, then they are great for keeping your fingers warm, but they are not the slightest bit waterproof.