Given that this is designed to be used in the unfortunate event of being caught out in the wilderness for the night without proper bedding, I have not had the opportunity to FULLY test it and I sincerely hope that I'm never in a position where I have to... but it's nice to know I have it if I ever do need it.
What I CAN comment on, however, is that as a bit of emergency kit, this thing's AWESOME.
It's compact and weighs practically nothing and it differs from the other SOL bivvies I've seen by being packed flat, rather than rolled, which makes it easier to put in a pocket or stow in a day bag - so there's no excuse to not be carrying this on a day hike.
There's an emergency whistle attached to the drawstring, which I was able to test - it's definitely loud .
Definitely an essential bit of gear, especially when you're "only going for a walk" and aren't planning on, or prepared for, an overnight stay.