I've been a PILE/PERTEX adopter for 40 years living in Carmarthan Wales, and 30 years in the Marine Corps deploying multiple times.
The Montane Smock has been my go to kit and is a perfect one piece layering system for high intensity "Winter" activities when the temps are near to sub zero conditions (skiing back country or on the lifts).
If the temps dive below zero (F) then a gore tex shell keeps me warm during an extended belay or on a long ski lift. Yes, it does not pack down like a down jacket, but it is light , breaths better than anything else on the market, wears like iron and never once was I wet, damp or cold as the PILE never retains moisture.
Bonus: the hood is brilliant and works under a helmet with no restrictions.
Better athletic fit than than a Buffalo Systems Shirt or Belay Jacket, and certainly warmer, ( Yes I have those pieces of Kit in my wardrobe).
I'm glad Montane brought this item back to the market. When you factor in the cost, it's a bargain.