I'm always on the lookout for products that make my pack smaller and lighter. I'll be writing a post on my process for doing that later.
For now, checkout the Ghost Whisperer down jacket from Mountain Hardware. Weighing only 7.7 ounces (7 ounces for the hoodless) and filled with Q.Shield™ DOWN 800-fill, this jacket is a legitimate piece capable of impressing the most jaded gear heads. Mountain Hardware's website suggests this "insulation resists moisture and maintains warmth." We'll see.
It certainly feels light and (because it's capable of stuffing into its own pocket) packs really small. As slight as it is, it's surprisingly warm. It's at least as warm as my standard weight North Face PolarTech fleece , but so much smaller. More down would make it warmer but, when used with a shell, can reduce the size and weight of your existing system. I use it with my Greenland No.1 Special Edition from Fjallraven and I've loved it.
This jacket isn't cheap, but I can't imagine a day that this jacket won't hold its own in my livery. That kind of garment never comes cheap. Mountain Hardware's MSRP is $350 for the hooded version and $320 for the hoodless.