One would be just as well off with light bivy items carried in the pockets of a jacket appropriate for prevailing conditions, and for a whole lot less money.
The Hilleberg item reminds me of what we used to call cagoules (or at lest the French called them by that term). They are a pretty handy garment, especially when supplemented with a few other things (garbage bags, space blankets).
_________________________
Geezer in Chief