I just got a Mountain Hardware Lamina 20 synthetic bag for bicycle and kayak camping. It comes with a compression stuff sack and packs down amazingly small. I've never seen a synthetic bag pack so small, will have to see how the insulation holds up, but it weighs 3 lbs. and compresses down to approximately the size of a football. The bag has an EN comfort rating of 23 degrees F.

I tested it out the other night with a low of 18 degrees F. in my Integral Designs bivy sack on a Therm-a-rest ProLite 4 pad, wearing heavy-weight fleece long underwear and a balaclava. I had to partially unzip the bag and sleep on top of the hood. Also needed to open the bivy up some more to let cool air in.

I plan on using it during milder spring and fall weather with my home-made hammock instead of the bivy, which is incredibly stuffy.

If I lived in a dryer climate I would love to have a down bag and I've always been set on one from Feathered Friends.