I was seriously considering one of the JRB wearable quilts for this coming year, but a couple of factors inclined me instead to buying a different sleeping bag --- a very personal trade-off based on personal experience and hiking + camping "style".

The key factor for me is that while I don't tend to spend a lot of time "hanging around" in camp, a lot of the time that I do so in cold weather I'm sitting "half in the bag" --- sober, in fact :-), but sitting up with my torso, legs, and feet in the sleeping bag, eating or typing up my trail journal or looking at guidebook and map pages to think a bit about the next days hike. In that context, I need something separate to keep my upper body warm, hence the JRB approach wasn't ideal for me. I also feel that an enclosed mummy bag is warmer per amount of weight carried than a quilt that doesn't enclose the head and neck. So instead I'm carrying a 6 oz down jacket "just for camp and breaks" and a warmer sleeping bag than I've ever carried before.

I definitely do NOT mean to talk down the JRB approach --- fine folks with a great product that fits some people's needs just perfectly, including some long distance hikers such as Andrew Skurka.

W.r.t. the candy bar in the sleeping bag comments, I completely agree with Lori. Outside of habituated bear areas (national parks and the like), I will sometimes sleep with my food, but never inside such areas. I personally met and talked (literally the following day) to a thru-hiker who had opted to carry more food than fit in her bear can and was sleeping on the remainder as a pillow when a bear came up to her in the night (I think she was cowboy camping) and initially let her know quite politely that it wanted her food. When she demurred, the bear put a paw on her leg, so she gave up the bag. Bottom line is that I would hydrate and eat just before sleeping but not sleep with food in the Sierras.