James M.wrote a review of Black Diamond Hooped Bivy Sack on December 23, 2009
First off let me say what it's been through, two years of wilderness patrol for the usfs along with a year on the trail crew and countless trips kayaking and snowshoeing. It's held up great. Also I'm known by many for being hard on gear. I typically will leave my pad in my bag in my bivy. This makes for a quick camp at the end of a long day. It's been thrown down on sticks, rocks, and other ruff surfacers all it's life... and it's still water proof.
You will notice some moisture on the floor in warmer wetter climates. Also the size is an isue for alot of people, but if you can put up with it, it's the lightest bomb proof all weather shelter you can get for a good price. It's also a bit hard to get into, like a sleeping bag with no zipper.
No doubt in my mind the best tent for the knees and the ultra light packer.
oh, you don't want to hang out in a bivy like you might a tent in bad weather or winter darkness.