I just bought an REI Expedition bag rated to minus 20. I already have a couple of good Marmot bags (esp. love the Helium), but this was on sale at 40% off (around $320) and had good ratings from people who used it at Denali, Aconcagua, etc. I've never had an REI bag. I went back to look at it again online and get a pic and it said it was sold out, so maybe I got the last one or something, or maybe they only made one.
I'm kind of wondering why I bought this, since I won't be climbing Denali or anything, but I'm getting ready to go stay through the winter in a poorly heated cabin that a friend's not using. I doubt if it will ever get below about 20, but if so, I'm ready. My dogs all have good warm bags, too (old well-used North Face and Kelty bags).
Shoots, I think I just wanted to buy something. What I really wanted is a new Tacoma with a Four-Wheel camper, but this will have to do. I also got some Gear Aid Tenacious Tape, which is great stuff for repairing sleeping bags and tents, if you've never used it.