Compressibility
The Storm King uses 650+ DownTek treated down and while it compresses into a medium sized compression sack, it does not compress as well as some of the other bags in this category.  

Warmth
The Storm King has a manufacturer’s warmth rating of 0F, but I found this too generous. I slept comfortably in this bag in temperatures down to about 25-30F, but was cold and had to add layers or a liner to sleep comfortably below 25 degrees. I used the Big Agnes Double Z sleeping pad as part of the Big Agnes sleep system—Big Agnes relies on the fact that its sleeping bag users will be using a sleeping pad, and does not insulate the bottom of its sleeping bags in reliance on the insulation from the pad. Although the pad was very comfortable, the sleep system did not provide adequate warmth, and another reviewer had the same result.  

Overall Comfort
The Storm King has a roomier contour shape with more room across the top allowing users to move around and side-sleep. These features provide extra comfort and room to move, but made it harder to heat up this added space in colder temperatures. I also find that not having down on the bottom of the bag makes it a bit less cozy for me. Overall comfort ran about the middle of the pack compared to other bags in this test.     

Durability
The Storm King proved tough and durable even after weeks of serious use. The bag handled tent condensation, the elements and winter camping well.   

Features
The Storm King was redesigned in 2015 with a roomier contour shape and more room across the top of the bag so users can roll over more freely. This created a more rectangular shape to the bag for active sleepers to get better rest and not feel constricted like in traditional slim cut mummy bags. 

The ergonomic hood provides more range of motion to move unrestricted while staying hooded and stretch fabric panels beneath the hood have a designated pillow pocket. The Storm King also uses DownTek treated down for protection from the elements, a vaulted foot box and an integrated pad sleeve to be used with the Big Agnes sleep system. The zipper on the Storm King also utilizes thick and stiff tape around the zipper, making the zipper smooth and nearly snag free.