Dorawrote a review of Marmot CWM Sleeping Bag: -40 Degree Down on May 8, 2017
Familiarity: I've used it several times
Not the lightest sleeping bag, but it kept me nicely warm when it was -17 °Celsius inside my tent on almost 6000m elevation. We slept with 3 people in the tent and there was some condensation on the inside of the tent. My bad kept dry, even after I spilt tea on it, and woke up the next morning and didn't make it outside for throwing up (sorry for the detail... high altitude sickness....). It kept fine, easy cleansing on the outside and the bag doesn't smell funny after all the usage.
I am 5' 8'' and in the regular size me, in my thinner down jacket and my clothes for the next day, innerboots and a few bits and pieces I didn't want to get too cold all fit in there fine (contact lenses, thermos, electronics). I haven't used it on a bivy, but I expect it to be perfect for that as well. NOT for summer camping, but worth the extra lbs.