I remember reading something a few years ago stating it would not work so well. Cant remember why. Maybe it was that it would not stuff well and breaks down. Cant remember. Makes a decent fire starter though.
You pretty much nailed it here. Also if it gets wet, it's heavy and doesn't dry out for a really long time, assuming it survives the wetting at all.
*Heaven best have trees, because I plan to lounge for eternity.
Good judgement is the result of experience and experience the result of bad judgement. - Mark Twain
As I recall from my boyscout days - WWII stuff was around in quantity. All kinds of stuff like this was used as filler in life jackets and similar uses but they sealed it in a plastic bag to keep it dry inside the canvas covering.