Fill Power: This is a liteweight discussion board, so a jacket (or bag) that will be lighter for the same amount of warmth is gonna be sought after. As mentioned earlier, many of today's top lightweight down manufacturers (WM, Nunatak, Feathered Friends etc...) now use very high fill power down. They also use lighter fabrics, and I wonder if this isn't where the 'flapping in the wind' confusion comes from. The down itself is warmer for the same weight, but the fabric is lighter and therefore less windproof. Lighter fabrics also have less intrinsic insulation to them.

For me I either sleep in a shelter or use a bivy bag for my bag, and windlayer on top of my other layers. This still works out to be lighter (for the same warmth) then using lower fill power down and heavier more windproof fabrics. If babybunny is not gonna use her Montbell jacket as part of a layered system for UL hiking, then it really is wasted money and she should get a heavier, lesser fill jacket. If lightening up is her goal, then she may need to master the art of layering. For three season use I go with polypro layer (180g), fleece layer (220g), Montbell UL down layer (240g), then wind layer (70g) for a total of 700g. For the forth season I use a Nunatak Skaha hoody with pocket (310g) instead of the Montbell for a total of 780. For this weight I have ultimate flexibility and warmth in all conditions compared to carrying just a single, heavier cheap down jacket. This kind of versatility and weight management may not be justified for someone who just goes car camping or wears it around the house...

Put another way, my first 3-season down/feather mummy bag (600fp) weighed 1.3kg. It kept me warm to around freezing, had a robust nylon shell, and a full zipper. When I finally upgraded, I went with a WM Ultralite that weighed 740g. It kept me warm well below freezing, used 850+ fp down and Quantum shell. The only difference I can find is in the weight, and at almost half the weight as the old-style bag, I would be silly NOT to change.

Actually, the bag I use now is a WM POD at 450g, but that would not be comparing apples to apples as the change in design is a big factor in the weight savings rather than just material and fill changes