I've owned the plain vanilla model of the Marmot Helium…
Fill: 850+ down
Temperature Rating: 15
Weight: 2 pounds 2 oz
I've owned the plain vanilla model of the Marmot Helium and recently decided to get this new EQ model in a slightly longer version. Marmot rates both Helium models at 15 degrees and that's a relative figure. Generally I think I sleep a little colder than the ratings of sleeping bags. I really like the full length zipper on the EQ (as opposed to the weight reducing 3/4 length on the standard Helium) as it allows me to open up the bag when in warmer conditions.
Like the Helium the EQ will compress to the size of a loaf of bread (I usually pack mine in a waterproof compression sack) and when it really gets down close to the 15 degree rating of the bag I throw in a Mountain Hardwear Compressor Coat and Pants and put those on. With that combo I'm usually good down to single digit temps with this bag provided I have a good ground pad.
The membrain or whatever Marmot calls the outer covering of this bag really is waterproof - I know I used it in a snow cave and it got a little warm and "drippy" in the cave but no water got through to the down. All in all a fantastic near-four-season bag.