This is a seriously comfortable bag. The stretch is effective, I think, allowing you to move while minimizing airspace when you're still. The material also contributes to the comfort factor, making it a joy to sleep in. I think the temp rating is probably right on. I just spent 5 nights in the Tetons and one night it got down just below freezing, and I was comfortable in this bag inside a 3-season tent with just a lightweight wool layer on and without even fully mummying-up. I do tend to sleep warm, but I think with extra layers I could push below the 25 degree rating in this bag. It's wonderfully compressible, too, taking up so little room in my pack. So far, I'm very happy with the purchase.