A quick question. I'm looking to purchase a zero degree bag and am confused by the various materials--goose down, hollofil, quallofil. What are the pros, cons of each insulation type? Any preference that you have?

Goose down is an efficient insulating material, when dry, but tends to lose that ability when wet. The synthetic materials hollofil, quallofil and others are similar products by different manufacturers and are reliable insulators even when wet. Pound for pound, I believe down has more insulating capabilities, but you need to keep in mind where you are going and how wet it will be there. A sleeping bag with 3-lbs of synthetic insulation is good for +25° to +35°. For zero degrees you will want an expedition bag with 4-5 lbs of insulation and probably an insert (kind of like an inner sleeve of thin material, sometimes cotton or synthetic), and likely a waterproof shell for rain and/or condensation protection. Most importantly get a good quality insulated sleeping pad that goes the whole length of your body, not the torso size. And also, wear socks, pajamas, and a knit cap to bed. If you get warm, zip the bag open a bit.