This has been a very useful addition to my EDC/camping gear for staying warm and keeping things (bugs, smoke, etc) off my face.  I would not solely rely on it for warmth below 30, but couple it with a wool cap and you're in business.

It is not square, which some have complained about.  This didn't bother me much, as you can still fold it properly.

I wear mine every day, and it has been through the wash several times; still running strong without a tear.