DonnOutsidewrote a review of MSR E-Bivy on August 31, 2017
Familiarity: I've used it several times
As one who has spent at least four nightlong pounding downpours in waterproof bivy sacks - whoa, check that, make it five or six or eight minimum given the '80s Sierra Designs Divine Light that just popped into my head - I never could get why my twin bro once had a North Face bivy that *wasn't waterproof.* What was the point? Well. Using the eBivy has shown me the point. The point is to put one lightweight shelter - your tarp or super-ultra tent - well over your head, and another one - that doesn't parboil you inside - around you and your sleeping bag, or even under you if conditions are allowing you to cowboy tonight. The eBivy is so light that you'll never be tempted to leave it at home. It gives you insurance against condensation; adds degrees of warmth - which may allow you to downsize your bag - to your sleeping system; gives you a place to stash gear up to and including your pack in the oversized hood (think 'pillow'); protects your pad from ground punctures; and will get you through most nights barring fullon monsoon conditions. If you pitch that tarp or ultra well, it might even get you through those; although I haven't had to test this yet, the floor fabric seems pretty bomb for the light weight.
Just had this along for two weeks in Maine with a decade-old 55-degree bag, which, maybe not in Maine, eh? My one-man tent handled precip. But the eBivy was the reason I got decent sleep on at least three of those nights. Warmth without parboiling; protection from the wet you didn't expect. And a little smidgeon extra priceless peace of mind. Just good to have.