I have a cold weather Gore Windstopper Bag, sort of a semi custom job, ironically made by the same people that made the old marmot bags in Grand Junction. It works very well, but is on the big / heavy side for most stuff. Most of the time, I pack a good solid 20 degree bag. I had been using a Feathered Friends Flickr , but recently got a semi custom Nunatak bag that on it's first outing worked really really well. I'd recommend a good 15 -20 degree bag, and there is nothing wrong with going lower in temp rating. I don't really care for the Marmot Helium, the zipper gets stuck way to often for my liking and the draft collar is non existent. Fix those two items and it would be a great bag. The FF and Nunatak both have center zips that are essentially snag free, which is certainly nice in the middle of the night, if needed and good draft collars.
