Works as advertised. Pricey but really small.. Works great...

I used the Atom so far just on summer hikes. Last weekend I trusted the weather forecast too much (low: 43F). At 6am it was 30F, and I was wearing long johns, a jacket, and a balaclava and was really toasty in the bag. I belong to the guys who easily freeze. It's the first time I experience a bag getting to a lower temperature than it is rated. I get my Atom, 4-season Therm-a-rest and all my clothes for three days in the lower compartment of my backpack. This sleeping bag is pricy but certainly worth the money.

The bag is not merely for ultralight cranks; I used it on a 5-day early-fall trip in New Hampshire with temps down to approximately 45F. Never cold. The bag was exposed to rain and dirt (never, ever use a tarp) but came through magnificently. The material feels like tissue paper but is very durable. The bag looks new after about a year of use. Loft is incredible; weight savings are great; but the real kicker is the packed size-easily down to Nalgene size. If need be, you could get it to about softball diameter. It starts a chain reaction of smaller (lighter) pack, etc, etc. The Atom is a great bag well worth the money.

I've been using Marmot sleeping bags for a decade, and they are well made and last. This sleeping bag is light weight (only a pound!), stuffs small, and is very comfortable. I bought it because my older 15-20 degree bag was always too warm for most of my camping, and I wanted to reduce the weight some. I used this bag several times in the mountains in late spring where the temperature ranged in the low 30's to upper 20's. Though the bag is only rated to 40F, with a silk sleeping bag liner, and wearing silk weight thermal underwear, I was able to sleep well. I was a little cold but I think that was due to the new sleeping pad I was trying out that was bought more for comfort (it didn't have an insulating rating because I suspect it doesn't really insulate). For all my summer trips where the temperatures been in the 40's or hotter, I've never been cold (even with that bad pad). I also haven't been too hot either which was always the problem with my older 3 season bags.

I recently purchased the Marmot Atom to bridge the gap between my REI travel down 45º and my Marmot Helium 15º or Feather Friends Swift 20º epic. At one pound the Atom rocks! I save 13oz from my Helium and over a pound off the Swallow. The REI travel down is actually 8oz heavier than the Atom and likely has more of a 50-55º rating. I have always loved Marmot quality and construction since buying my first Pinnacle 0º in 1992, which by the way is still in near-perfect condition after hundreds of nights. The Atom is built with the best materials and down available. The construction is top notch. I particularly like the hood design which wraps your face with a comfy baffle. At 40º this is a warm, roomy and cozy bag. You could easily push the frost level with a light layer of clothing worn inside. I recently used the Atom at 6,500ft on Mt. Hood on a summer hike. The weather was warm, but it dropped into the low 50's or upper 40's at night. We were at snow level and pitched my tent right next to the slowly fading snow field, which added to the coolness of the night. I was quite happy in my red cocoon. The color is great and adds to a warm tent glow. At one pound I would be hard-pressed to find a better bag! Thanks Marmot!