It works like it should. The liner has nice room in it if using with a larger bag or rectangle. Light weight and packs down small with inlc stuff sack. I typically leave it inside bag and roll both up together to eliminate yet another stuff sack.. havent measured to see if you get a full 10 degrees more out of it, but it definately adds noticeable difference.
This review was written in the old system and had content requirements that are different than reviews written today.