Interesting that Rab describes the ultra bivy as made from "Pertex Quantum Endurance" fabric. There is no such thing. It's either Pertex Quantum, or it's Pertex Endurance. PQ is very breathable, but not very waterproof. PE is not claimed waterproof, but it has a membrane and will withstand a > 1000mm water column, so it's a lot closer. Would be nice if someone could verify exactly what Rab is using. My guess is that it's actually Endurance.
[Edit: There may be such a thing as "Pertex Quantum Endurance" after all (see below), but there is no mention of PQE on the Pertex website at http://www.pertex.com ]
The E-wing is a great looking tarp, but too short to provide full coverage in my opinion. It's ridgeline is less than 7.5 feet long from point to point when pitched as a A-frame, and it's sides slope in from there. You could fit your gear in alongside you though. You might be okay with your feet sticking out in light rain if the Rab Ultra Bivy is made from Pertex Endurance, but you'd have better coverage with the MLD monk tarp.
Q: How does pertex endurance hold up to rain and the ground? Condensation? Will I want a ground sheet?
A: No personal experience with PE, but it would seem borderline without a tarp overhead and a groundsheet underneath because of the relatively low water column rating. Condensation will be more than with PQ, less than most other membrane fabrics. Some condensation is unavoidable in a bivy under the worst conditions.
Q: What would your suggestions be for a so see-um option to accompany this set up. I'd like to keep it super light and more of a drape/bivy type enclosure so I can move in the summer when I'm not wrapped up tight in my bag.
A: It's possible to sew a piece of no-see-um netting into a bivy. I prefer to attach it along the top of the opening and leave the rest loose. When you need it, simply pull it down across your face and tuck it in. This will leave the netting draped on your face, but you can tie it up with a short piece of cord if this bothers you.
Q: Will I hate myself for not getting a bivy that closes over my face?
A: You will not need it to close over your face if you use a tarp. Closing a bivy over your face is a miserable exercise anyway, as the humidity and condensation become unbearable quickly that way.
Q: Will I hate myself the first time it rains?
A: Maybe. A bivy without a tarp is possible, but not much fun. Without a tarp there is no where to get out of the rain, dry things out, and hang out.
Q: Will this be appropriate for winter backpacking; I plan to use a marmot lithium bag.
A: Yes, very appropriate, assuming the temperature is within the temp rating of you bag, plus clothing worn, and with a minor contribution from the bivy.
Q: Last but not least how do tarps hold up in the wind?
A: Depends. Catenary cuts are made to shed wind. Judicious staking also helps. Tarp material matters too.
