Great price on GoreTex. I'd want to know what the bottom was made of, too. (Probably coated nylon, but it never hurts to ask.)

In that same price range, if I were looking for a bivy, I'd also consider the REI Minimalist. It's about a pound lighter, full side zip, and has a mesh panel over the head and neck area. However, it's a proprietary W/B fabric (Elements?), and there's no W/B cover over that mesh opening. So, it's designed for use with a tarp, not out in the open on its own. However, a good product at a good price - before lightweight tents (like the MSR Hubba line, Big Agnes offerings, and TarpTents) came along, I used a Minimalist a lot with a tarp. Now, I'd never even think about using one.

You made an excellent choice with the Moment, given what other folks are saying and the general reputation of TarpTent products.