I have slept in the AMK Bivy once. Wasn't planning on it, but, one of the boys had a sleeping bag float down a river after swamping the canoe. (Lash everything to the canoe, how many times did we tell them that??) <img src="/images/graemlins/crazy.gif" alt="" />

I had a sleeping bag, and also had the bivy in my daypack. The youngster got the sleeping bag. I put on an extra layer of fleece, and used the AMK bag for the night. It actually was too warm. (This was a fall night, but, not really very cold, and no wind.) The bag had a nice feature I never expected I'd use until I was a little warm, there is a vent at the bottom, so you can get a little airflow around your feet, and keep the moisture going somewhere. The vent has a velcro closure. I did have a closed cell foam pad with me, so it was a pretty cushy set up. Normally I'd expect to have to improvise some kind of leaf bed under me.

I have always carried some kind of emergency bag or bivy in my daypack for hikes. I try to remind the boys that when you go out in the woods on a day hike, there are circumstances that someday may turn it into an overnight, so be ready for it. I no longer bother with the space blanket bag, because they are so fragile. They would be better than nothing, for sure, but, for only a little more bulk, I have something that's pretty usable, (and re-usable). I haven't used the heat sheet, so I can't really compare it.