I own the vest version of this coat. It weighs about 12.5 oz. (size large). I think it's under-filled--there are areas with no down at all. I have actually thought about opening it up and filling it with high-quality down, since the shell itself seems pretty light, but tough, and the fit is good for me.
For the use you mention (throwing in the vehicle for emergency), it would be great, but it's pretty heavy for the warmth it provides. One other downfall is that there's no DWR coating on the fabric, so water soaks right in. For these two reasons, I never take this backpacking anymore, and hesitate to use it as a layer when it's snowy or rainy.
I have had mixed results with Cabela's brand gear. Most of it is way too heavy, and I've had to return quite a few pieces of clothing and other gear because of premature wear or some other quality issue. Their packable flyrods are great, though, for the money.