Favorite bag I've ever owned.
Marmot has a terrific product here, I usually go to Marmot for all of my down products, and this was no exception. It's extremely light weight, compresses down into the stuff sack very easily, and could be compressed more if you wanted to buy a compression sack for it. Has definitely kept me warm in 0-10 degree situations with minimal or no layers on. I haven't had to test the waterproofing of the MemBrain technology as I keep my down products extremely dry all costs, but I have faith in it. I have had some heavy dew on mornings when I've slept out of a tent, and there was no issue with the bag.
I really have nothing negative to say about this bag, and will continue to use Marmot almost exclusively for my down products.