Lots depends on what bitter cold means to you, and what you'll be doing.
I like down. But be aware of the downsides. Like rePete said, don't get it wet. Don't wash it or dry it the wrong way. And depending on the shell material, you might find that feathers stick out and get lost.
Also, wearing a shell over a down jacket is great to keep out water, but remember that it will also partially compress and not insulate as well.
The worst part of down though, is the field repairability. When a down jacket gets a tear, it can lose feathers quickly. If you're relying on that loft, you'll have to carry a patch (maybe duct tape, if you don't care about looks). Sewing a small hole is possible, but expect the down to escape during the process (without the patch, that is).
I wouldn't suggest a down jacket for an everyday jacket, but they can work OK if you're careful. In the winter I use one for when I'm just standing around in below freezing temps.
For everyday wear, I'd choose a jacket with a zip in liner (I think Jacob recommends this either in the book on on this site as well). A nice thick three layer breathable shell fabric is versatile. Then a zip in liner of either wool, fleece, or something like primaloft makes for a flexible system. Go with a vest and thick balaclava if the temps get really cold.