Now that the down DWR "revolution" is upon us I have much more faith in down as an all-around insulator.
My "ideal" winter sleeping & in-camp insulation solution:
SLEEPING BAG:
-20 F. DWR down bag with a zippered expansion gore parallel to the main zipper (for making room for wearing insulated clothing to extend the bag's range W/O compressing the bag's insulation)
CAMP/SLEEPING CLOTHING:
Western Mountaineering-style Flash DWR down pants and jacket and down booties (Pants and jacket worn in camp and for sleeping if the bag's range needs to be extended)
This combo of bag and insulated clothes has been used by many so it's not "rocket surgery" but the new down DWR innovation has, IMHO, made it a much more viable alternative and may even put off the need for a VBL liner to much lower temps.
"Multiple use" is the byword for lightweigt backpacking and using insulated clothing to extend a winter bag's temperature range seems a no-brainer. I have used my Thermolite Ultra insulated jacket and pants in my 30 F. WM Megalite bag to go down to 15 F. and slept very cozily. DWR down seems the next logical step, that is until "UltraTherm" synthetic down comes along… ;o)

