perfect in a bivy
I've used Thermarest pads for years but decided to give the Big Agnes a try. Better loft, better comfort, and a better fit in a bivy sack

Good size, not too big
Nice warmth and smaller than a closed cell foam pad. Fit well into my pack with other winter backpacking and mountaineering gear.

Great Sleeping Pad!!!!
I used an older air pad before and it was cooold and bulkier. Although you'd be hard pressed to squeeze this down to the size of a nalgene, it's still more compact than most self inflaters. It's super warm! I laid on it in my skivies and was warm to the touch and seemed to hold my heat well! I was happy to see that it came with a stuff sack also!

great product
works well and keeps you warm, it is worth its weight to bring it along

Keeping you warm at night
I used the Big Agnes dual core insulated mummy pad with a Big Agnes zero degree bag and have had great results. I have used it on two separate winter camping trips where the temps have dipped into the 10's and single digits. One particular night dropped to -3 and yet the pad did its job of keeping me warm from the cold ground. I did toss and turn a little that night but I believe that was due to the warmth of my bag and a need for an additional layer of clothing rather than from losing heat through the pad. I love the fact that it combines the comfort of an air mattress with the insulation of a closed-cell foam pad. I have used only this pad on my winter camping trips and have left my closed-cell foam pad at home. I own one other air mattress and I would need to bring the foam pad as well if I wanted to stay warm at night. This is not the case with the dual core pad which helps on reducing weight and pack space. It also fits perfectly into my Big Agnes bag which prevents me from rolling off my pad in the middle of the night. My only dislike is that the valve will blatantly leak air if it isn't accurately screwed on tight. In other words, there have been two different times that I have closed the valve up and yet air was still clearly leaking out of it. I would have to reopen the valve and make sure that the threads were not cross-threaded and that there was an exact seal. I haven't had this problem on my other air mattress. Regardless, once you get the hang of the pickiness of the valve, the pad will hold its seal all night and keep you warm. All in all, I would recommend this pad to others. Happy camping.