Brett Clatt wrote a review of The North Face Inferno Sleeping Bag: 0 Degree Down on April 24, 2014
Familiarity: I've used it once or twice and have initial impressions
Used this for a hike/camp up to Longs Peak on 4-19-14. Temps got down to 10 degrees. Used the sleeping bag, silk liner and a thermorest 1" self inflating pad inside of a Trango 2 tent. We camped at 11,500' on snow, and I stayed warm enough that I had to keep the bag 1/3 unzippe so that I didnt over heat in it. I easily trust this bag at 0 degrees and IMO you could go lower with the proper liner.