Don W.wrote a review of MSR E-Bivy on October 9, 2012
Familiarity: I've used it several times
Nice dry desert trip and I wanted a bivy to add a little warmth to a lightweight sleep system and protect from dew, or spatters of light rain. It would do that, but so would a plastic bag. Soaking wet inside from condensation. (no, i did not breathe inside the bivy.) Temps dipping below freezing.
I tried a couple of nights and then returned it as soon as I got home.