My wife has the an Arc Teryx Alpha SV - it looks seriously overbuilt. www.verber.com and linking through to Mark's outdoor clothing page has a LOT of great information on it, including the possibility of using a vapor barrier shirt beneath the insulation. This seems to be very useful in very dry, very cold conditions by keeping a moist humid environment right next to the skin, and allows the insulation to remain dry and effective. This would also make the breathability of the outer shell a moot point. I have not tried this combination with the vapor barrier, but it makes sense.

Eric