I made the mistake of not understanding that Fill Power is not the whole story of a jackets insulation/warmth ability. This jacket is so light it could struggle to be a very effective liner. I knew it was a lighter duty jacket but had know idea that 850 fill power could be that light. I accept that I was not knowledgeable on the "fill power" rating system, and should ave done more homework. But there really should be a better system to tell you exactly what the full warmth ability of an article of clothing is.
This review was written in the old system and had content requirements that are different than reviews written today.