I just received my JRB Mt Washington 4 last night. I strung up the double-nest, attached the quilt, popped in and threw on the Marmott 0F bag as a top quilt. Temp was 32F with a 16mph wind this afternoon. No doubt that this will be the *hot* ticket on my upcoming winter hike in 2 weeks!
It was so comfy (just had jeans, regular pair of socks, and a north face zipup on) that I fell asleep for about an hour and 40 minutes during my test.