We're working out what we think - we'll add our view here!
Mountain Hardwear says:
A sustainable reimagining of our best-selling ultralight down jacket, the Ghost Whisperer™ Pants layer effectively under ski pants, perform efficiently while warming up at the boulders, and even pack into its own pocket after you take them off. Because something's off if your belayer's shivering like they've got Elvis leg. Why put all the focus on layering around our core yet miss an opportunity to lock in heat around the lower half of our body? This is our solution.