Winter sleeping bag recommendations?

I'm looking for recommedations on a good winter sleeping bag and information. I'd like the lightest weight and the best warmth for the dead of winter into the springtime if there is such a bag. 0, 15, 20 degrees? Synthetic vs down? Outermaterial? I'm just starting to look into buying one and with so many choices i'm looking for any experienced people with overnights in the winter to help me out. Thank you!

Overstuffed Feathered Friends 10F.

Lots of threads on NWhikers, TGR, etc., but I'll post a few of my quick thoughts to get you started.

If warmth/weight ratio is the biggest factor, that says down insulation right away. This also suggests a superthin material, but they can be fragile, so be careful. Gore/eVent membranes are also an option for a few extra ounces if you're going to be in a moist environment and/or aid with an emergency bivy. Temp rating depends on what conditions you expect to see and how warm you are as a sleeper. For only one bag to start with, I might recommend something in the 15-20 degree, perhaps the FF Swallow or WM Alpinlite (a couple extra ounces for slightly wider cut and a draft collar). Something in that range will generally suffice for PNW winter conditions with a down jacket and a well insulated sleeping pad, all while being not too unbearably warm or heavy on the late spring/summer trips. As suggested above, Feathered Friends and Western Mountaineering are two of the top brands in the business and the extra $$ is very well spent IMO. On the more mass-produced side, Montbell, Rab, and Marmot seem to make decent stuff too. Some people will probably suggest a quilt-style, but I don't think I would recommend it if you're just starting winter camping and don't know how you sleep yet.

Personally, I have a WM Antelope GWS and I'll soon be picking up a Summerlite to save 1.5lbs when I don't need 0 degree capabilities.

For PNW winter camping, what about using your three season bag plus some down or primaloft pants and jacket with hood. If nothing else this approach makes getting up at night and in the morning much more comfortable.

For a zero degree bag I have the NorthFace Snowshoe and really love it. It's a zero degree.. It's a bit heavier (like 3.5#'s) but it does get the job done and I've used it from -20 to 50.

I also just picked up the REI flash sleeping bag and that thing is 1# 7oz and compresses to almost nothing, I could probably fit the whole thing in a nalgene bottle compressed. Give you an idea, I compress that, and my thermarest air-bed to the size of a soccerball in a compression sack.

Testing the REI flash tonight when we head to St Helen's. I'll give you better reviews after tonight.

Overstuffed Feathered Friends 10F.

^^^This. I'm a cold sleeper and I have a FF 0°F with event and it's very comfortable for me down to 10°F. I also have a 20°F bag for spring, but I tend to bring the colder one when temps drop below the high 20's. The only small issue I have with FF is my bags don't tend to compress as well as comparable bags. With that said, I don't plan on parting with mine any time soon.

Three more recommendations:
-Don't try to be ultralite and survive with a 20°F bag. The extra lb of bag and insulated sleeping pad is well worth the weight, so skimp elsewhere.
-Your sleeping pad choice is more important than your bag.
-Don't bother with synthetic. If your sleeping bag is getting wet you're either out for more than 3 nights in very poor weather or doing something wrong.