User Review: The North Face Dark Star -40
Fill: Polarguard Delta
Temperature Rating: -40f/-40c
Weight: 4 lbs. 12 oz. (long size)
Price Paid: $235 on sale
I took this bag to Denali and returned with all of my fingers and toes; I never had a problem sleeping. The positive features of this bag: very warm (though perhaps not as warm as I expected); light for a bag of this warmth; beautifully designed and constructed, with all of the "bells and whistles" (e.g., fully adjustable hood, good draft protection, watch pocket, etc.); no down to get soaked in wet/humid weather.
Negatives: quite bulky (though I was able to keep the upper hand with a large OR Hydroseal compression sack); only moderate loft; reportedly mediocre durability (e.g., supposedly the loft will diminish markedly over time).
Unless you are willing to shell out $500+ for a Feathered Friends, Marmot or North Face down bag, this is one is a no-brainer for trips to Alaska and other cold destinations where you can tolerate a little bit of extra weight and bulk in exchange for economy and comfort.