WorldClassGear.Com wrote a review of Marmot Aiguille Sleeping Bag: -5 Degree Down on May 22, 2003
Based on my experience so far, the Aiguille is comfortable from about +35 to -10 degrees, depending on what you are wearing while sleeping. It is a great three season (fall, winter, and spring) bag, as long as you don't do any extreme winter camping.
While the shell material is very water-resistant, it is not waterproof, so you will need some protection from the elements, such as a tent or bivy. In cold weather, moisture buildup in the bag should not be any problem, but toward the warmer end of the scale, 30 degrees and up, the bag can build up moisture inside. The best way to deal with this is to vent it with the zipper.
If you spend a lot of your time on cold weather outdoor adventures, and you need a bombproof sleeping bag, you can't go wrong with the Marmot Aiguille.