Regarding the Adventure Medical Kits (AMK) Bivvy Sack: I faced this decision not too long back. For me, it was either the Land/Shark or the AMK Bivvy and I chose the Bivvy, mostly because it was so much lighter and, as near as I can tell, more compact. Lighter and more compact was important because the Bivvy is a woods-EDC item for me and assumes I am caught without my full-size backpack and tent. The Bivvy strikes me as a good balance between the lighter, too-fragile emergency shelters (e.g., Space Blanket) and the heavier, more robust Land/Shark. There are quite a few on-line reviews of the AMK Bivvy, and they helped sway me…

http://www.backpacker.com/gear/article/0,1023,2261_P,00.html

http://www.backpackgeartest.org/reviews/...Field%20Report/

http://www.backpackgeartest.org/reviews/...Field%20Report/

http://www.backpackgeartest.org/reviews/...Field%20Report/

http://www.backpackgeartest.org/reviews/...Field%20Report/

Since I only recently received the AMK Bivvy, I haven’t had a chance to test it myself.