I recently purchased the bag and am happy with it so far. I haven't tested it down to 15 degrees yet, but it's definitely a well made product. It's fairly heavy, but I wasn't prepared to spend the money for something lighter and this is a good compromise as it compresses fairly well into the bottom of a 45 litre backpack. The main thing is that it's very roomy for a mummy style bag. I turn a lot and am a fairly restless sleeper, and it doesn't feel restrictive at all to do that in this bag like some of the bags can.
The slip for attaching it to a sleeping pad is a good feature as well, although it's necessarily a bit loose, so whilst it's better than not being attached, it is still possible to slip off the edges of a 20 inch pad. A good feature though.
This review was written in the old system and had content requirements that are different than reviews written today.