We also did some testing with the bivy bags. I used the 2.0 and my wife the smaller version. It was at Hawk Mountain, PA last September. The temperature was around the freezing mark and we had no sleeping pad just a woolrich jacket beneath us. We both slept pretty warm, quite uncomfortable without a pad but we kept warm. My wife slept in her clothes and I put on a light pair of fleece pants and shirt. I did get a little condensation the first night but the second night I open the bottom up a little and had no problem.
My opinion is that these make a great emergency bag and we will always carry them. They will not replace a good sleeping bag but they could very easily save your life.
Marty Simon