Most livable bivy for the weight
Background: I live in the PNW, backpack ~50 nights a year in all seasons, and sleep mostly under a pyramid shelter. Because I hunt, I spend a lot of time camped in bad weather. I've used two bivies from other cottage manufacturers over the years to keep drafts out of my quilt—I prefer to not have condensation under my shelter so I pitch it high, and I prefer to not have to cinch my quilt down in order to stay warm.
Anyway, this is probably the best water resistant bivy you can buy. It's very smartly designed, easy to get in and out of, is light, and looks well built. If you're looking at other more traditional bivy designs for sleeping under your tarp, don't. Buy this one.