I just used this bag for 6 weeks straight while backpacking through the high sierra this summer (2004), above 10,000 feet most of the time experiencing nighttime temperatures between about 25 and 55 degrees F or so (guesstimate). I absolutely loved it. I am a 5'-4" 125 lb female and tend to get a bit cold easily. I never even had to cinch down the hood or draft collar. A bonus worth mentioning is that they make a small size, which fits me perfectly in length and has enough space around the torso that you don't feel clausterphobic (they also make a regular and long, I believe). It packs really really small and is unbelievably light. It is less than half the weight of my previous down bag that I used for 14 years. A possible down side is that part of the reason it is so light is the fabric. We were in a 3-season tent every night, so the sleeping bag was not subjected to much abrasion. It seems very thin, not like something you'd want to be dragging around in rocks and twigs, but then again I didn't test it. It could very well be quite strong fabric but is SEEMS thin. Also, I did notice that feathers seem to pop thru more frequently than they did with my old bag. On the positive side, the internal draft collar is cozy, and the draft tube along the zipper has a nice thick fabric strip along it so the zipper doesn't catch on it. Highly recommended if you are looking for an ultralight warm bag.