I own the Western Mountaineering HighLite sleeping bag, a 16-ounce goose down bag rated for 38 degrees. One way Western got the Highlite so light is that it has a half zipper. I love this bag dearly, but sometimes find that the half zipper pulls apart in the middle of the night when I get up for a bathroom break. How can you not wake up while trying to get it back together? I hate that.
Western has announced the SummerLite sleeping bag (pictured below), which for 3 ounces more gives you a full-zipper and is rated for 32 degrees. I believe the longer zipper and extra warmth justifies 3 extra ounces.
Another feature: fully baffled with insulated draft protection.
Says Western Mountaineering: "We designed this bag for the lightweight fanatics who provide us with feedback, criticism, and motivation to continue producing the lightest down products available. This bag will debut this spring in limited supply to selected retail partners. It will become available to all WM dealers by Fall (2006)."
Be light. Be safe. Be one with the pack.