I've played with many of them (designs and brands) in several terrains/environments. I'm starting to think that I like a shelter just a bit bigger than a single hoop bivy, roughly the size/weight of an ID MK1-lite plus a small tarp, pitched separately from the tent. It seems like the best of both worlds.
You can walk around with a roaring fire with your skeleton fully extended and in case of rain, duck under the tarp. When it's sleepy time, then into your clean/dry/down insulated sancuary to wile away the hours with the sandman/book/ipod/dreams of a massive rack (purposely ambiguous). The MK1-lite plus a Silwing tarp is 4.5lbs. If you are using it as a one man shelter (which I do) you can use the "other" side for the damp/dirty stuff. I think if a second guy was along, I might move up to the MK3 size, and a little larger tarp.
That's what I'm going with for now, check me later for a newer opinion.....
