As a top layer, the only thing I can think of is continuous activity in the cold, either moving on skis or bike, or activity in cold wind. By cold I mean below freezing, like XC skiing or snowshoeing in squeaky dry snow. They are heavy and have very little loft.
Worthless in the wet or snow at/around freezing temps.
Heavy for what they are.
I used one, once, on a wet high hunt in WA's north cascades. Never again, in 13 years of gram-weenie hunting from the Brooks Range to the Lee Metcalf, early August to late November.
I think you'll get more use out of a light puffy vest for cold activity (Patagonia puff or similar weight/loft) than a softshell, as it serves the same core windblock purpose in the cold, and won't accumulate snow on your shoulders to melt and wet out. I've certainly used mine that way, and it augments a puffy jacket well with very little added weight and noise (no rustling sleeves).
In cold snow, if dayhunting from the road, a filson jac-shirt or similar would do the same things better, yet would still be useful in precipitation at/around freezing.
