Used it in -20, only had my socks and a light next-to-skin layer on. It was perfect, even a little warm, had to pull down the zipper on the side. Packs well into the sack it comes with it. Waterproofing really works, stayed completely dry on the inside.

I have owned this sleeping bag for two years. It is one exceptionally warm bag. Loft is super. The hood really keeps the heat in well. Pull cords some times annoy. They need to be shifted from time to time.Developed a small rip in one of the seams. Needed to have it repaired at a local shop. Almost impossible to stuff into sack provided by marmot. Needed to get a bigger one!

I used it a couple of times this winter mostly below 0F.
Tried it at Longs Peak Boulder field with Bibler Tripod bivy and The North Face Himalayan Jacket and no sleeping pad (wind took care of that one)... I am not sure about the wind chill outside it was below 0F in the bivy. I would not need the Jacket if I had the sleeping pad. Sleeping bag is roomy and very warm... The only problem is the stuffing sack (which I did not even try). I got an x-large OR compression sack. Even that one needs some work... I also have a Helium. I think The North Face Himalayan jacket and helium is the light-weight alternative for me.

This is a great bag for cold winter camping. This sleeping bag is amazing warm and lightweight. I was happy with its loft as soon as I pulled it out of the box. The features of this bag make it ideal for any cold, extreme climate. I think its waterproof cover is a necessity for winter camping. This bag is great and I would recommend it for anyone who needs a super warm winter sleeping bag.

I couldn't believe the loft of this bag after I pulled it out of the storage sack and fluffed it a bit. When I first got it out, it didn't look too impressive. After a couple minutes though, the thing had ballooned too a massive cocoon. I like how Marmot put the majority of the loft on the top of the bag, where it can keep you insulated. The down doesn't really do you any good on the bottom of the bag, since it is just smashed under your body anyway. The hood is a little smaller than I would have liked, but it's not a huge deal. I especially like the waterproof/breathable shell material of the bag. I can't imagine ever being cold in a bag like this. Top notch bag, but you definitely pay for it.