I just bought the British army mvp (moisture vapour permeable) 'sleeping bag cover'. I had been uneasy about being 'exposed', but equally I wasn't enthused by the 'coffin tent' idea of a looped bivvy. The decisive factor was that I wanted protection for my Arctic down sleeping bag, protection from both condensation and rain, especially as I won't be able to air the bag on extended trips. My eventual choice should protect better than a closed looped bivvy, where condensation from your breath can form. Plus my choice is considerably lighter, is quicker to get into, and, usefully in some terrain types, it has a smaller ground plan. A mosquito veil (head or full body, I bought both used from a local army surplus) and good tarp (same) still add up to a lightweight 'sleep system', and make for a great 'outdoors' experience. All beautiful equipment. The only real drawback is that from the comfort of my home I still shiver at the thought of being exposed.