I am the Vice President and brand manager for Sierra Designs. So I guess you could say that I am "affiliated"....;)
I see comments focused on the hood design and hand pockets of the Backcountry Quilt, but what makes this quilt truly special is the size.
First, I should say that our philosophy on lightweight is slightly different than many of the cottage brands. To us, the whole goal of going lighter and simpler is because lighter and simpler is MORE COMFORTABLE. When lighter is LESS comfortable, we think the goal is lost, and we stop. I understand that for some, hitting a certain number is important for performance or whatever reason. But for us, comfort is the goal. Light is the means to the end.
That said, in our opinion, most available quilts are simply too small to be comfortable, and specifically, way too short. Because of this, they almost always require additional clothing (usually a down hoodie) to address this, minimizing some of the weight advantages, and narrowing the usable temperature range. Mostly, this additional clothing is required to insulate the head and neck, which traditional short quilts fail to do.
We wanted to make a quilt that allowed comfortable side, stomach and back sleeping in a wider range of temperatures, without having to carry an extra garment (and associated weight) to extend the comfort range. A quilt that someone who was suffering in a traditional mummy would try and use, and transition to a more enlightened approach to their sleep system. And in order to do this, we needed to insulate the head.
When you sleep in a bed at home, and you get cold, you naturally (without waking) wrap your covers tightly around you. If it gets really cold, you naturally wrap the quilt around the back of your head too. So while the hood is indeed the head insulating solution for back sleeping, the solution for side and stomach is the long quilt itself, simply wrapped around your head like a bed at home. So if you NEVER sleep on your back, I agree that the hood is not a value added feature. (That said, some testers do use the hood in other sleeping positions.)
Way more important than the hood feature, is the "hand pocket" which creates a natural un-sewn baffle that folds the side of the bag inward, helping seal out side drafts. The hand pockets allow for very simple manipulation of the quilt, and natural wrapping of the quilt without having to grab. You don't need this at home because the quilt at home is so large, but on these narrower designs, it makes all the difference.
Finally, I find it funny that anyone would refer to Sierra Designs as a "big brand", because our new team rallies around our common disdain for the big brands, and the products that they make that we truly just don't like. We are getting into quilts and beds not because we want a piece of the action (there honestly currently is not enough business there to make it worthwhile), but because we believe they are simply better ideas than the tired old status quo. We certainly don't want to negatively impact the cottage industry, that is currently driving virtually all the new ideas and smart thinking in the market. If we have our way, new-better-different ideas, and the brands that drive them, "cottage" or otherwise, will flourish. Tired old big brands and the sea of sameness is where we want to take our marketshare.